1. The contract is valid, but it must be returned. However, you can recourse to the bank and let the bank bear part of the responsibility.

2.a In this case, people are also guaranteed. Is there any false operation when applying for a loan? If so, the bank can sue A, and the first point is invalid.

In fact, I don't think the second loan is illegal, because the first two guarantors C know it is a normal loan. A handles the second transaction, which belongs to the nature of mutual insurance. A should also get the quota, which belongs to profit. If it is mutual insurance, A will naturally be responsible. In addition, A can't prove that he doesn't know about B's loan.

Your question should cover up some unfavorable situations for A.

So this loan must be repaid, and A will lose the lawsuit. But the house will not be auctioned because there is no mortgage. You will only be blacklisted, and banks generally won't go to court to auction your house because 654.38+0.5 million, because 654.38+0.5 million is too small.