loosen power and the oil light came on

Jon Jon, If you can now turn the engine over by hand, it does sound like the engine is not locked up. But if the oil pump failed or you ran the engine low of oil and continued driving when oil light came on there could be internal engine damage/wear. Did the first mechanic say whether the engine was low on oil or pump failure or why he felt engine had locked up. If car is not starting and you can not trust what the first mechanic/shop told you, get a 2nd or even 3rd opinion. The shops may have to pull oil pan or use video scope to see/verify what damage's are done and to what extent. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.