Getting refund from builder

On 7/2/13, I signed an agreement with builder where the clauses were 1. I had to pay 20% of flat cost(which I paid same day via check). 2. For other 80%, I had to take a loan and bank had to disburse half of loan amount immediately to builder and other half after 1 year. 3. In event of cancellation builder will refund 100% of the amount paid by me till that date. Inspite of me taking loan from LIC, builder didn't take funds for next 6 months. In between a circular from RBI came restricting banks to give such schemes. LIC said maximum it can disburse is 25% of loan amount. So it was decided on email that first I should instruct LIC to disburse 25% and then on completion of 6th slab next instalment of 25% will follow. Till now builder has not constructed 6 slabs in my tower. On asking for cancellation and refund he is saying that since he didn't receive 50% of loan amount as mentioned in AOS he is not accountable to the agreement. Important points to note are : 1. AOS is not registered but it is signed by all parties on Rs 100 stamp paper. 2. On cancellation, the agreement does not mention time frame of refund of money or any interest that had to be paid by builder. 3. I had expressed my concern on slow progress of project many times on email and builder never raised the point of not receiving 50% loan amount before. My questions are: 1. Can I approach State consumer forum to get refund? If yes, what would be approximate cost of litigation and how much time it generally takes. 2. Even if consumer court rules in favour of me, can builder delay payment by challenging its decision in higher courts? 3. Is builder correct that not paying 50% of loan amount upfront absolve him of any liabilities from breaking the agreement? 4.There are around 50 more persons who have a similar case. Will it be beneficial to jointly pursue the case?