If a player has a card that says instant on it, they can play that card at any point in the game, even if its not their turn
Now, not every card is available in every treatment, so I'll start with a look at the various booster products and how they are structured, then do a style-by-style breakdown of where everything can be found
A +4/+4 when they swing is just powerful for your tokens
The other ability, which costs two loyalty counters, flings a creature and draws cards if that creature was a hamster
Zipfolio offers good protection from most of the worries you might have about your collection and has a zipper to keep unwanted stuff out and ensure your cards dont accidentally spill everywhere
Refurbish is going to be our best option, based on its cheap cost and the potential to also a act as a pseudo-flicker spell in scenarios where we decided to sacrifice the Jewel through Oswalds ability