Russia withdrawing to 2013 borders is a pretty absurd possible diplomatic solution. If Russia withdrew to the stalemate of 2020 with no discussion would the Ukraine actually risk reopening the entire hot war again or try to find a manageable level of tit-for-tat skirmishes?
Certainly Russia would prefer to try to reachieve that stalemate than enter a discussion that arrives at 2013 borders..
Perhaps in a situation where it was actually diplomatically solved and Russia actually wanted to accept 2013 borders there's something else on the line that is far more important than anything in the conflict.
But realistically, most ends to the hot conflict probably will end in suspicion and a continued stockpiling of arms by both sides.
I don't think anything will be resolvable until Putin is politically incapacitated and a replacement possibly doesn't see the conflict as worthwhile for their own political needs.