Assignment Agreement

Hi, Builder ( A Party ) First Owner/Assignor ( B Party ) Assignee ( Me/C Party ) 1. B party booked a flat in 2015 from A party(builder) and went into a sale deed. B took a loan from HDFC for this flat and by Jan2018 paid complete consideration to A. EMI is getting paid by B. 2. In 2018, B wanted to transfer the property to C 3. C paid advance to B on a sale deed/MOU . B paid transfer fee to A. 4. A, B and C did a assignment agreement on stamp paper in favor of C. A transferred the property right to C. 5. C applied for the loan in HDFC to pay the consideration to B (The original sale deed of B is also in HDFC against his ongoing loan) 6. A has no dues left and property is ready to handover. Registration date not yet confirmed by A. 7. Builder mentioned in the assignment agreement that B have to witness as confirming party mandatory at the time of registration. Now the problem is: 1. B may not come as confirming witness at the time of registration once he receive full consideration from C before registration. 2. Registration is delayed and have no dates yet. 3. B is requesting consideration amount from B, but the C's loan cannot be disbursed before registration My Questions are : 1. Should C wait till the time of registration to pay to the consideration to B. How to safeguard C? 2. What will happen if the time passes and the registration gets delayed. 3. B has to wait? or can give power of attorney to the builder as an excuse not to be present at the time of registration. 4. Is B's presence mandatory at the time of registration by law? 5. Bank is considering this property as under construction even its ready to handover and people are already started staying in the society. And for the reason they will give the home loan to C only on pre-emi till registration. Please help!! Thanks Nitesh