Is this a grey area in Indian marriages? Lawyers kindly advise

Suppose A (woman) marries B (man) under HMA. They have a child X. Later, A and B divorce with mutual consent.

A then marries C under SMA, a man who has an existing wife and kids already. C and his first wife never had the paperwork done, but their social marriage was done in a religious place and their society sees them as husband and wife. C does not divorce her before marrying A.

Later, B realises he needs his ex-wife A on paper for pension and general ease in society. With her consent, they register themselves as married again.

In this hypothetical:

1. Is A and C's marriage valid, since C did not divorce his first wife?

2. Is A and B's remarriage valid, since A had earlier married C?

3. If A files for divorce from C, would it raise any alarms anywhere and potentially affect B? As it's a weird scenario for any system.

4. Can C and his kids legally try to claim X's inheritance, though he had no financial contribution to it? X has no paperwork linked to C.

5. What would be the best course to clean up a weird scenario like this and protect A, B and X?