AFAIK, ELCA bylaws state that if a congregation leaves, they (the congregation gets to keep the property. There have been cases I’ve heard of where ELCA has still tried to keep the property, though.
Correct on both counts.
Part of the procedure for congregations departing states that congregations which were either part of the LCA before the 1988 merger, or formed subsequent, must receive the approval of the Synod Council.
In a few cases the Synod Council has refused dismissal on the grounds that the congregation is "critical for mission". There is one such case in Wisconsin that has turned into a very ugly court battle.
In a few other cases the Mission Investment Fund of the ELCA has demanded that any outstanding loan balance be paid in full before dismissal.