If I use Grand Tree to evolve from Charmander into Charmeleon and then into Charizard ex, can I use Charizard ex's "Infernal Reign" Ability or not?
No, you cannot use Infernal Reign because Charizard ex was not played from your hand to evolve Charmeleon.
Source: TPCi Rules Team (2024-09-26)
If I use Rabsca's "Revival Blessing" attack to put Charizard ex onto my Bench, can I use the "Infernal Reign" Ability to search for and attach up to 3 Basic {R} energy?
No you cannot, because Charizard ex is not being played from your hand to evolve 1 of your Pokemon.
Source: TPCi Rules Team (2024-06-27)
If I use Rare Candy to evolve Charizard ex, can I use its "Infernal Reign" Ability to search for and attach up to 3 Basic {R} energy?
Yes, because Charizard ex is still being played from your hand.
Source: TPCi Rules Team (2024-06-27)