You’ll have to feed live at first, and may have to for its entire life. I was able to wean mine on to frozen but it was difficult and took a lot of patience. Even once they’re eating frozen live food should be fed regularly. I fed mine every other day. They’re probably one of the most sensitive lionfish out there, I had one for over a year and lost it due to a minor wound that most healthy fish would have recovered from easily. Because of this I would seriously recommend keeping it alone, theyre very fragile and all it takes is a little stress or minor injury to kill them. Something as simple as another fish nipping it’s fins can lead to a disaster.
If you want to keep it with other fish, I think an antennata or another lion would be a better choice, the antennata looks similar and is a similar size but is much hardier than the radiata. As far as treating lions goes, they’re generally pretty resistant to stuff like ich, but not immune, so I’d just quarantine anything wet that’s going in to the tank to minimize the risk of introducing a disease, since treating lions can be such a slippery slope.