I may have to meet a potential husband for my sister. How should I learn about his aqeedah? Can I ask about specific sins? e.g if my sister doesn't want someone who likes music, is it ok for me to ask him if he listens? can I tell him about some of her sins that he may dislike and not want from her?

Ustadh AbdulAziz al-Haqqan

You can ask questions regarding his deen without a doubt, so that she doesn't marry someone who is upon deviance and sins. Also, if he asks u, u should answer truthfully