From Sayed Sistani's risalah
Issue 14: If a person performs his acts for some time without taqlid of a Mujtahid, and later follows a
Mujtahid, his former actions will be valid if that Mujtahid declares them to be valid, otherwise they will be
treated as void.
https://www.sistani.org/english/qa/01208/
This takes 5 minutes, if you want to find out the Shia opinion on something don't just ask random people on facebook, ask someone in real life or do some research...