Otherworld has been referred to as a multiversal realm throughout literally all of excalibur and even the infamous surtur otherworld feat, I have no idea where the universal stuff came from, specially when the citadel exists in otherworld.
them fighting galactus doesn't mean much, all that happened is that a well fed mind you galactus killed one of them with brute force and they merged and 1 shot him. Even adult franklin richards who is >>>> galactus needed power from his young counterpart to fight the super celestial. Also it would be bold to just assume that hickman didn't have the UN and galactus as either equal or galactus as superior
all the statements you need are
here , he made this pretty good blog awhile ago.
the doppelganger scan works fine for me and I can justify it,
idk if this link would work for you
Making one universe at a time actually doesn't mean anything, lets not forget the fact that the superstructure statement would still be 2-A regardless of range as it wouldn't make sense they'd just create every universe one by one unto transinfinity lol, franklin was portrayed as 2-A throughout the entire storyline (secret wars)
for the griever the griever quite literally respects and admires franklin's power, and she is irrefutably a threat to the multiverse.
the super weapons the celestials created (the exterminators and the death seed) both got forcefully sealed by the celestials, the weapons aren't entirely superior to them, this both means the death seed scan and the other scan are valid