A few Questions

[Switchc2390]

Can you retreat more than once a turn?

Also, if you're making a deck, can you put in more than 4 of the same special energy in?

Thanks.

[PokePop]

No, the rule that you can only retreat once per turn was added in 2003.
Note, though, that using a Trainer like Switch does not count as your one Retreat.

You are only allowed to have 4 cards with any exact name.
So that means only 4 Darkness Energy or any other Energy card with a Name.
Basic Energy cards, you will notice, have no name printed on them, so you can have more than 4 of them.
Also, it has to be exactly the same name.
So you can have 4 Metal Energy, 4 Darkness Energy, and 4 Dark Metal Energy if you want.