When Welder is used to attach 2 Fire energy, does Old Cemetery trigger once or twice?
Any energies attached from the hand would trigger Old Cemetery, once for each energy card being attached. So in this case you would put 4 damage counters total.
Source: TPCi Rules Team (2022-01-20)
If I have Miltank with the "Moomoo Malt" Ability as my Active Pokemon and I use Welder to attach 2 Fire Energy cards to a Benched Pokemon, does it heal 90 or 180 damage?
Any energies attached from the hand would trigger Moomoo Malt, once for each energy card being attached. So in this case you would heal 180 damage.
Source: TPCi Rules Team (2019-05-09)
Can I use Welder if there are no Fire Energy cards in my hand?
No, you cannot. You must be able to attach at least 1 Fire Energy card in order to use Welder.
Source: TPCi Rules Team (2019-05-09)
If I use Welder and attach a Fire Energy to an Eevee that has the "Energy Evolution" Ability, do I draw the cards for Welder first or search for a Flareon due to "Energy Evolution" first (or is it a choice)?
Since they are simultaneous actions, it is the player's choice of which order they can do this.
Source: TPCi Rules Team (2019-05-09)
If I use Welder to attach {R} Energy to my Pokemon, do I still get to use my one energy attachment for the turn?
Yes, you do. Doing something via an effect does not use up the normal actions you get during your turn.
Source: Unbroken Bonds FAQ (2019-04-19), TPCi Rules Team (2019-05-02)