Marrying a married women

Q: I married a girl and she was already married to a guy. For the last 4 years he was in a jail due to some reasons... The family members doesnt have any information about their son. And his wife also dont have any information about her husband whether he is coming out or not. There was no information at all regarding her husband so we had done nikaah. Is it right or wrong? Is she still married to her first husband? Her husband was calling from jail and he was not saying whether he was coming out or not. Now after 4 years he came back to India. What must do?

Women facing their toes towards the qiblah during sajdah?

Q: In salah I mistakely thought women were supposed to point both toes towards the qibla in sajdah because I felt like I remembered reading an instruction which said that. My feet were both on the ground horizontally, however the toes were towards the qibla. I’d like to believe my past prayers were ok? Are prayers ok even if women follow the man’s way?

Dating

Q: Is it permissible to get a nikaah and get to know the person? A term called halaal dating?