Africa is certainly an "adventure destination" that one should visit at least once in their lifetime. I've been there several times, twice on vacation (2000, 2005). Let me chip in a few words here from my experience.
1)for trips like this, what would be the minimal number of days required?(got to plan leave)
The longer the better. If visiting only 1 or 2 places, I think 10 days is enough. If your itinerary is more ambitious, then I think you can easily spend 4 weeks which you allow you to cover the grounds at a more leisurely pace. If you can get 16-18 days leave, you can have a lot of flexibility with the itinerary. Don't forget that you will already use up 2 days flying between SGP and South Africa. If you go other places like Botswana, Zambia, etc, you may fly domestic and more days are eaten up again.
2)is a big mama lens always required?what should be the minimum focal length to bring?
I assume you plan to shoot the wild life in the safari parks. If so, a BIG MAMA lens is great to have. One major consideration is the kind of tour being done in the safari. Essentially there are 2 types - a) sitting in the 4 wheel drive vehicle b) walking safari. If you are on the vehicle, you can get very near many of the animals. Sometimes as close as 10m (eg. lion resting). In this case, a fast 70-200mm zoom with a 1.4x teleconverter may be all you need. However, on a walking safari, you cannot get close to the animals. Either the animals keep their distance, or you want to keep your distance because of the danger. Typically this distance may be 100m. So you want to bring your 400mmF5.6 tele lens or better. For my trip, I brought along both a 80-200mm zoom and 200-500mm zoom. The longer lens get used about 80% of the time, and 2/3 of the time was at 500mm end.
Oh, make sure you bring a decent pair of binoculars (8x40 or better).
3)i heard there wont be electricity in certain parts of the stay.so exactly how many days without power and how many batts should we bring to be sufficient?
Some of the camps are operated in a very rustic manner and design for low environmental impact. These camps do not have mains electricity (solar power may be available). So I suggest you get 3 days worth of batteries for your camera. Although you may be in the park for several hours daily (usually 1 early morning trip, 1 late afternoon, 2~3 hours each), your shooting is occasional, not continuous. So turn off the camera after shooting to conserve power and typically 1 Li-ion battery for DSLR should last a whole day. The flash gun is very seldom used, so you can leave this out if your backpack is already overloaded. It's good to check ahead if the camp has mains power.
4)what kind of accomodation will we be looking at?tents?rovers?any 5 stars hotel?
There are 5 stars camps, but these cost an arm & a leg. If money is no object then OK. Many of the camps are build with trees/bamboo/reeds/canvas and intended to non permanent. Even so, the beddings are generally of good quality (clean mattress, bedsheets, pillows). Food are also of good quality and quantity (mostly western, grills)
5)is this kind of trip constantly ongoing to different places or you can dump your luggage in a hotel, and make the day trip and then back to hotel in evening?
The one that is constantly ongoing is a kind of cross country safari which is based on a very large all wheel drive vehicle. This thing can take about 20 people including all luggages, tents, cooking equip, etc. It goes from one site to another (mix of landscapes, villages and safari parks) across a few countries. Typically it runs from South Africa (Capetown up north to maybe Tanzania and back). One way trip can take up to 16 days.
The other kind of safari camp requires to travel to the camp and stay there for a few days (3~5 typical). You bring all your stuff to the camp. For the daily park tour, you bring only your camera/lenses and water bottle. Some of the camp also offer a truly back to basic field camp in which your guide will bring tents, food, cooking gear and you stay out in the park for 1 or 2 nights. In this case, you bring only your basic essentials and leave your main bag in the camp. My suggestion is to bring only 2 bags. One is camera backpack, the other is all your barang-barang in a soft trolley bag or backpack with wheels.
You bring only outdoor gears - 2 outdoor pants, outdoor field long sleeve shirts with UV prot, dry fits and T-shirts you can use then throw away. 1 pullover in case it gets cool. Wide brim hat is a MUST (nylon/soft). If you have a day to spend in Capetown on your arrival, they have very good outdoor gear stores where you can get all the good stuff at reasonable prices.
6)any dangers?(sounds stupid but i'm more concerned about health issues and being robbed)
In general, it is not dangerous to walk about in African towns during the daytime. The local people are generally friendly and very interested to talk with visitors. Of course there are areas that you shouldn't go, just ask the locals about this. Don't wear fancy watches or jewelry.With regards to the safari tours, you must follow the instructions of the guides who are also responsible for your safety. You do get a lot of safety briefing. For example, you should NOT wander about outside your tent in the night. If you need to pee in the middle of the night in the tent, learn to use a zip lock bag or similar contraption.
7)recommended vaccination?and how many days/weeks/months in advance that we have to take it before the trip?
You can go to Tan Tock Seng Hospital Travellers Clinic and get all your jabs there. You should go there 1 month before the trip. If I recall correctly, they can only give you 3 jabs on the same day, so if you need to have more than 3, you must make another trip down there a week later. Depending on the places you intend to visit, the clinic will make the recommendation for the jabs to take. Usually include Yellow Fever, Typhoid, HepA/B. There are varying opinions about taking Malaria pills before the trip. TTSH will certainly recommend you to buy and take the malaria pills from the hospital's pharmacy. However, in Africa, I have been advised not to take the pills as a precaution. This is because the pills are not effective against all forms of malaria. So, the logic is if you get hit, it is better you get sick and show true symptoms so they can prescribe the right medication to take. In both my vacation trips to the safari parks in South Africa, Zambia, Botswana, Zimbabwe I've seen very very few mosquitoes. Certainly no more than anywhere in SE Asia.
8)cost per pax for entire trip?
Excluding the flights between SGP & Africa, the local expenditure can run around US$100~200 per day.
9)any self drive 4WD with GPS system?
Yes you can rent vehicles in South Africa to drive around the normal roads & towns. If you do, buy maximum insurance cover. But you can't drive it into the game parks.
10)when's the best time/season to go?and how's the climate like?as hot and humid as sgp?
The cooler season is more green. Plenty for the animals to eat, but they have a lot of vegetation to hide behind also and harder to spot. The hot season is dry, not so humid as Sgp, the land is more yellow/brown/parched, the water sources are smaller, but the animals are easier to spot since there is less cover. What you are able to see is also a matter of luck since the herds do move around alot especially in the large open game parks.
11)any personal contacts, lobangs?(if inconvenient, please pm me)
It is not difficult to plan your own itinerary and do it Free & Easy instead of booking a standard tour from travel agents here. There are lots of info on the internet. A lot of African tour operators are based in South Africa and do have websites.
12)other than animals and birds, is there anything else in that country that's worth a visit?
Besides the wildlife, Africa do have many other attractions. There are varied landscapes such as Vic Falls, Kalahari desert, Orange river water rafting, the very pretty Capetown, etc. I find the villages to be very interesting - the mud/straw houses, loads of smiley kids though they look scruffy, cottage industries, etc. English is widely spoken in many areas, so talking to the locals is interesting too.
I will hesitate about an all ladies group visiting Africa on backpacking style. Good to have some guys go along.
