Most Ph.D. programs take 4 years to complete, but it depends on the student. I've seen them done in 2 years, and I've seen them take 5 or 6 years, or even longer.
NTU isn't a bad school, but it's not a tier 1 school either. It would be easier to get accepted into a program there but NUS would be a better choice (assuming you could get accepted into either school, which given your lack of simple research skills isn't a given).
haha yea, my lack of research skills will screw me over, best not to go ahead then!