Are you asking me if I believe that God Himself is unchanging through time (and outside of time) or do I believe that God's actions within time are unchanging?
I do not see that much of a difference in the questions Pony...If you have a God that arbitrarily changes His mind..how can you rest on His promise of salvation? He may change his mind
Mal 3:6 For I [am] the LORD, I change not; therefore ye sons of Jacob are not consumed.
Hbr 6:18 That by two immutable things, in which [it was] impossible for God to lie, we might have a strong consolation, who have fled for refuge to lay hold upon the hope set before us: