Learning French in Belgium (Brussels)

I'm planning take a French Course from Beginer level to Advance Level with fully payment of tuition in advance, (A1 - C2, in Alliance Francais). Is it possible to obtain Visa for whole year (approximate period to complete the course)? Cos, I know that Alliance Francais only allow to enroll for the period of 4 months only (able to extend).
Or I obtain Visa for first 4 months in Belgium Embassy in VN , and extend in Belgium?

Any advice and assistant woule be highly appreciate.