Married a girl when she was minor what is the validity of marriage

I have married a woman in 1988. She was a minor when i married her. I have two children(a boy and a girl) with her who are now majors. And in 1992 I left her not through a divorce from court but through registrar office. She has signed that she doesn't want any alimony from me. and from then we have been living apart. It has been 24 years. I remarried in 1993 and have two children(two girls)(majors) with her also. Now, my first wife is threatening me that she will file a case against me according to 494 section though I have been sending her money every month from many years. What should i do now? Is 494 bailable? I am from Andhra Pradesh. Can i claim my marriage void as it has been more than 24 years? or void because she was a minor? What is my responsibility on her children? What will be the situation of my second wife? can my first wife file a case on my second wife under any section? I live with my second wife. Please give me suggestions.