Ac lines won't make a difference to rear heat. They're 2 separate loops running to 2 separate heat exchangers tucked in the RR quarter panel. Temperature control is carried out by airflow switching between the two - blend doors.
However, rear blend issues are relatively common on these vehicles and that WILL cause issue.
Also of note, if your a/c lines are blocked, I'd address that sooner rather than later. They don't block for no reason. Either there's a compressor failure... Which you should sort. Or there's some stop-leak stuff in there that gummed up the system, which should be addressed before it causes more damage.