Convert from CP to AOS for parents

[lc_cheat_victim]

I'm a US citizen and applied GC for my parents through CP in 2018 when they were in India. I130 and proof of support documents have both been approved and they're waiting for the interview for last 15months. There's no sign of that happening. My parents are really old and can't afford to wait. They do have a  10year multiple entry visitor visa that expires in 2025. Can they enter US with that while they await the interview? Assuming they do, what's the procedure to convert from CP to AOS? 

[JoeF]

A visitor visa does not allow immigration intent. They clearly have shown immigration intent. If they travel with the visitor visa they risk being denied entry. Besides, there is a travel ban for visitors from India.