In niagara falls,ny does a landlord needs to paint walls and change toilet seat before new tenants move in

If they are damaged or have normal wear and tear, yes.

Check with your local permit and codes office.

Did you walk through this unit beforehand? Have you requested this work be done? Whether it's oversight, or non compliance, the first step is TALKING to the landlord, after you have reviewed your lease carefully. (You may have signed off with your initials, or they may have an extended time to get the work done). Take a few pictures also.

I found no specific laws that made painting and a toilet seat replacement MANDATORY on a state level, locally may be different.

Short answer: no.
You are being ambiguous anyway. Can't tell if the landlord promised those to be done but didn't say when he'd do them, or what your story is. Or even if you are the tenant or landlord.

Maybe