Whenever I hack key items onto to Pokémon ds-3ds era, it lets me take the item. If the item is in the generation but not in the game, it’ll have the description while in the bag but remain unusable. I haven’t tried items that aren’t in a generation, though. It also wouldn’t let me trade the Pokémon holding the shiny charm (gen 7). This is what X remembers lol
I’ve done the shiny charm, poke radar, and eon ticket, a few other event items too. I can’t prove the shiny charm worked, but I got 4 full odds shinies within like 10 hours of gameplay (oak challenge)
Let me know if this is a good enough of an answer; I can add the exact examples and times I did this
I won’t be able to test past 3ds era. My hacking software is good, but it only supports gens 3-7 as of right now. If there’s anything in particular you’re curious about within those gens, like any specific items, lmk