Per regulations, ASA certified bats are allowed in the NSSL. ASA recently merged with USA. So USA and ASA bats are allowed on the field of play.
Absolutely not! From 20 years to 0 days, the NSSL is for all skill levels.
The USA softball rule book can be accessed here
Check out the by-laws and rules of governance here
And here is the NAGAAA governing manual, just in case.