Can I have 4 Teal Mask Ogerpon ex, and 4 Hearthflame Mask Ogerpon ex, etc. in my deck?
Yes. They are all different names.
Source: Twilight Masquerade FAQ; TPCi Rules Team (2024-05-23)
If I receive cards in a Prerelease prior to the expansion set's release date, can I use cards from that set in a sanctioned tournament as long as those cards are reprints of already legal cards?
Per the current Play! Pokemon Tournament Rules Handbook you cannot use any new cards until the set is considered legal for tournament play (currently the 2nd Friday following that expansion's US market release date), however you can use a newer version of a reprinted card that is currently playable in the Standard or Expanded format immediately upon its official release.
Source: TPCi Rules Team (2022-08-04); TPCi Rules Team (2024-01-25)
Can I evolve the Cleffa from Obsidian Flames into Clefairy?
No. Cleffa doesn't say that it can evolve into Clefairy, and Clefairy doesn't say that it evolves from Cleffa.
Source: Obsidian Flames FAQ; TPCi Rules Team (2023-08-10)
Here's some info regarding Pokemon ex: • Older cards that refer to Pokemon-ex should include modern Pokemon ex. Pokemon-ex and Pokemon ex are the same. For example, "Gardevoir ex" from EX Sandstorm has the same name as "Gardevoir ex" from Scarlet & Violet. • Pokemon ex from the SV series have a Rule Box, but Pokemon ex from the original EX series do not have a Rule Box. • Pokemon ex are not Pokemon-EX. For example, "Gardevoir ex" from Scarlet & Violet does not have the same name as "Gardevoir-EX" from XY-Primal Clash. Case-sensitivity matters.
Source: TPCi Rules Team (2023-04-06)
Beginning with the Scarlet & Violet expansion, "Pokemon Tool" will be its own category of Trainer card; Pokemon Tool cards will no longer be printed as Item cards. Pokemon Tool cards from all previous series will receive errata to align with this change, meaning that older Tool cards are no longer considered as "Item cards".
Source: TPCi Announcements (2022-12-12) [https://www.pokemon.com/us/pokemon-news/2023-pokemon-tcg-standard-format-rotation-and-pokemon-tool-errata]; Scarlet & Violet FAQ; TPCi Rules Team (2023-03-30)
Can I evolve my Unown [V] from the Neo or Diamond & Pearl series into Unown VSTAR?
No, you cannot. Unown [V] is a different card name than Unown V.
Source: TPCi Rules Team (2022-11-10)
If I have a heavily damaged Basic Pokemon V in play, can I use Thorton to switch it with a regular one-prize Basic Pokemon from my discard pile?
Yes, and if the new Basic Pokemon has less HP than the amount of damage counters it is immediately KO'd and will relinquish only one prize to your opponent.
Source: TPCi Rules Team (2022-09-29)
Can I make an entire deck with jumbo sized cards to be used in a sanctioned tournament as long as they are all the same uniform size?
No, you cannot. You may only use cards that have been released for TCG play in the standard size. Jumbo cards are artistic representations of the legal card's art.
Source: TPCi Rules Team (2022-08-04)
If I have a confused or poisoned Genesect V with 2 Fusion Strike Energy attached, and my opponent has a Cradily with the "Swaying Strangle" Ability in play, would I be able to Retreat after I have discarded the 2 Fusion Strike Energy cards as the cost, or would I no longer be able to Retreat?
Since you began the Retreat process while Swaying Strangle was prevented by the Fusion Strike Energy, you get to complete the action and Retreat even after discarding the 2 Fusion Strike Energy cards. The behavior is also similar with Flygon's "Labyrinth of Sand" ability or Snorlax's "Block" ability.
Source: TPCi Rules Team (2022-03-31)
If I use a VSTAR Ability can I also use a VSTAR Attack in the same game?
When you use a VSTAR Ability or Attack you flip over your VSTAR marker. Once that marker is set, you cannot use another VSTAR Attack or Ability during that game.
Source: Brilliant Stars FAQ; TPCi Rules Team (2022-02-24)