Abilities » Rebirth
What happens if I try to use Ho-Oh EX's "Rebirth" Ability but my bench is full? Is the Ability used up, or is it not used and I can try it again later after I have some space on my bench?
If you know the Ability will not affect the game state, you cannot use it. If your Bench is already full, you cannot use Rebirth.
Source: TPCi Rules Team (2016-06-09)
Abilities » Rebirth
If I flip heads for Ho-Oh EX's "Rebirth" Ability, if I only have one Fire and two Lightning energy cards in the discard pile, can I take all three of those?
No, you can only take one of each different type of energy, up to three total. So in this case you could only take one Fire and one Lightning.
Source: Dragons Exalted FAQ (2012-08-23), TPCi Rules Team (2012-08-23)
Abilities » Rebirth
If I have two Ho-Oh EX in my discard pile and flip tails for "Rebirth", can I flip a second time?
You can flip once for each Ho-Oh EX in your discard pile, but each coin flip is treated individually.
Source: Dragons Exalted FAQ (2012-08-23), TPCi Rules Team (2012-08-23)