I haven't played for a very long time...

[Gymnotide]

... and I have a lot of questions that need answering.

Question 1: Since there are two 'Mysterious Fossil' cards, do we treat the old one as the updated one (probably not)? Holon Phantoms has a 50HP one, but the ones before only have 10HP.

Question 2: Can you place a fossil or Poke'doll as a Basic Pokemon on the first turn? Can you do this even if it's the only Basic Pokemon you own on the first draw? Can you mulligan in this event?

Question 3: Is there a card that nullifies one of your own Pokemon Powers until the end of the current turn without ending your turn? Preferably if this Pokemon is a Grass/Water/Colorless or is a Trainer card.

Question 4: What's the recommended amount of energy cards / basic Pokemon / evolved Pokemon / Trainers you should have in your deck? I know the minimum and maximum is 60, but what proportions?

Question 5: Poison & other special effects are removed when you retreat, right?

I think I'll get myself a new avatar & sig now.

 

[Marauding Master]

... and I have a lot of questions that need answering.

Question 1: Since there are two 'Mysterious Fossil' cards, do we treat the old one as the updated one (probably not)? Holon Phantoms has a 50HP one, but the ones before only have 10HP.

We treat them as the updated one, if you use an old one in a tournament then you MUST have a new one next to it(Not in your deck) to show what the updated version says. but Mysterious Fossil sucks so don't worry.

Question 2: Can you place a fossil or Poke'doll as a Basic Pokemon on the first turn? Can you do this even if it's the only Basic Pokemon you own on the first draw? Can you mulligan in this event?

No. No. You have to.

Question 3: Is there a card that nullifies one of your own Pokemon Powers until the end of the current turn without ending your turn? Preferably if this Pokemon is a Grass/Water/Colorless or is a Trainer card.

Not until the end of the turn but if you want to negate Pokémon Powers then I recommend Cessation Crystals. They might be hard to come by though.

Question 4: What's the recommended amount of energy cards / basic Pokemon / evolved Pokemon / Trainers you should have in your deck? I know the minimum and maximum is 60, but what proportions?

Go for 10-15 Energies. 25-30 Trainers and 15-20 Pokemon. Going under or over is okay, depending on your decktype. However Trainers are definitely your best cards.

Question 5: Poison & other special effects are removed when you retreat, right?

Yes.

I think I'll get myself a new avatar & sig now.

Here, I answered your questions.