Yes, it can.
You previously ruled that
Captain Ironhide can't use his Bot Mode ability to swap his weapon for an
Energon Axe if he is undamaged. Does this also extend to other Upgrade movement effects? Does this mean I can't use Quartermaster or
Private Red Heat to move an Energon Axe in play from a damaged character to an undamaged one?
[Source: WotC]
That is correct.
Energon Axe can only be put on damaged characters.
Optimus Prime - Battlefield Legend will get the +3 attack, but since the weapon with the very long name was attached after he began his attack, the ability will not trigger and you will not be able to scrap any cards to add to your attack.
Can Quartermaster be used on Sergeant Cog? If not, is there a way to revive Cog from the KO/discard area for use again?
[Source: WotC]
No, and not currently…
Why is it you cannot increase a character’s attack with a reattached
Battle Master during an attack, but you can increase
Optimus Prime - Battlefield Legend’s attack if you flip an action like Leap into Battle? How is this any different to using OPBL’s skill to play Quartermaster and attaching a battle masters upgrade form before defense flips?
[Source: WotC]
You can use Quartermaster to attach a KO’d
Battle Master to OPBL. If OPBL’s ability results in a weapon being attached to him (for example via Quartermaster), the attack bonus of that weapon will apply because you haven’t counted attack yet. However, if the weapon gives the character bold, bold will have no affect because you’ve already flipped battle cards.