US Immigration from Lithuania

Hello!

Haven't been here in a while and kinda lost the plot.
Wife has 2 year green card, and this month is our 1 year anniversary. Originally came here on K-1. We need to remove conditions and as far as i know, researched before, we can file N400 and I-751 together, and have one interview.

Can we still file those two together to have a combined interview? Hope nothing change since my last visit here.
What is the time window to send in those forms? (1 year, 90days before the expiration of GC?)

Do the checks have to be separated for each form? (assuming yes)

The proof of relationship is the usual stuff, Lease, insurance, 401k, photos etc. Right?

Everything else seems fairly straight forward and less of a hassle paper-wise than AoS or K-1.

Probably a redundant question - if this was recently answered - i'll delete my post

Thanks!