Yes. It is the compulsory part. However, you may ask the company to make thefull-range contribution and you still contribute 5% only.
i don't think so...
you can only increase your part say up to 20% from the first year, not your company's part. of course if you are citizen, you'll get 13% from the company. if you are working in gov (including NUS) you can also get 13% from the start.