I am seeing either some questionable rule claims or else some questionable wording.
The physical TCG has Unlimited (all sets legal), Expanded (
Black & White and later releases legal), and Standard (
XY: Kalos Starter Set and later releases) Formats.
Lysandre's Trump Card is banned I think in all of these formats, but for sure in Expanded and Standard.
Shiftry (
BW: Next Destinies 72/99) is banned for Expanded play, but legal for Unlimited. Should you try the Pokémon TCG Online (the official TCG program owned by TPCi), there is an additional Constructed Format, the Legacy Format; it consists all all
HeartGold/SoulSilver series releases,
Call of Legends, and
Black & White series releases (nothing is banned).
If you're using an official format, then know that to properly use older cards you need to
- Know the current game rules and terms
- Know the game rules and terms from when that card originally released.
The big confusion comes from three things
- Evolution of game rules and mechanics
- Reprints with updated, game relevant text
- Errata
The first turn rules have changed over the years; if you're using older cards to play in the Unlimited Format, just know that you cannot attack first turn. Everything else goes; decks in Unlimited are often designed to win first turn by dedicating themselves to bounce effects (ensuring your opponent is left with one Pokémon in play), and methods of damage counter placement (to KO that last Pokémon without attacking). Or at least this was the case the last time I messed with it; that was years ago and I would be happy to be wrong.
The core card types have changed, then changed back. From
Base Set until
Diamond & Pearl we just had Pokémon, Trainers, and Energy cards. There were many subdivisions within these cards, but all cards fell into one of these three types while in your hand or deck (some could be more than one while in play, IIRC). With the release of
Diamond & Pearl, it was decided that we would go from three to five core card types: Pokémon, Trainers, Stadiums, Supporters, and Energy. Stadium and Supporter cards predate this, and were originally just a subdivision of Trainers.
This continued until the release of
Black & White, at which point Stadium and Supporter cards were rejoined with Trainers, and a new subdivision for Trainers was added (Items). It was ruled that any Trainer card from before
Black & White that was not a Stadium or Supporter would be treated as an Item, and all new Trainer cards were either Items, Stadiums, or Supporters. The non-Trainer Stadium and Supporter cards released while there were five core card types (instead of three) were also ruled to count as Trainers of the correct type (Stadium or Supporter).
When a new card is released that is meant to be a reprint of an older card, the older versions are to be played as if they had the text of the newest version. If the text is significantly different, the older version either cannot be used, or can only be used with a copy of a current version for reference (I can't remember off the top of my head which). Some cards have also received errata officially changing the text of all older versions.
*whew* So what does all that mean?
Professor Oak is played as if he was an Item. Yes,
Professor Oak is functionally identical in effect to the current Supporters
Professor Juniper and
Professor Sycamore, but it doesn't matter: he is played as if he was an Item. You can play multiple copies of him in the same turn, and you can use him even if you've already used a Supporter, etc.
Bill was most recently re-released as a Supporter, during the period when Supporters were
not considered Trainers. If you use any
Bill now, treat them as both Trainers and Supporter cards.
Potion now heals 30 damage instead of having you remove two damage counters. "Healing" is now an officially recognized mechanic, distinct from just moving (and removing) damage counters. An errata was issued for this.
Switch is treated as an Item, but I think you can still use copies from
Base Set because the actual effect text is close enough.
Professor Elm is played like he was an Item, but he prevents you from playing
any additional Trainer cards. He was
not released during the time when "Trainer" in card text should be interpreted as "Item".
Junk Arm is treated as an Item, and its effect that allows you to discard two cards from hand to reclaim a Trainer from the discard pile
actually only can get you an Item; while it says "Trainer", it was released during the time when Supporter and Stadium cards were their own thing. With such cards, you treat "Trainer" as if it read "Item".
Computer Search... I know we got a ruling for this but I still can't remember what it was. Based on everything else, the older copies for it should be treated as Ace Spec cards as well, meaning in Unlimited you could only have a single
Computer Search. Yet I think the two are treated as separate cards, so that you can still use four of the older
Computer Search cards in your Unlimited decks. Please, if someone knows the correct rule for this one, let us all know.
Anyway, with all that said an old school Haymaker deck is probably losing to most modern cards. While the older deck would have an easier time setting up and disrupting the opposing player, Haymaker's big weakness was a deck that could set up attackers capable of OHKOing Haymaker Pokémon. Mind Games (
Neo Genesis Sneasel and
Slowking) could probably still prove strong.
It still is a great game and it's still also going VERY strong!