Help verifying (or fixing?) a traded Pokémon

[Opal]

I've got a Pokémon I received in a trade from a friend a few years ago, they themselves got it through wonder trade. I kind of always assumed it was hacked. The friend has since passed on, but it eventually made its way onto my team and it's incredibly dear to me now. With Z-A on the horizon, I'm worried about it's legality/if I can safely transfer it out of Violet and into HOME or other games.

The problem is, and no worries at all if this means it's not worth your time, I do not have a hacked Switch, nor do I have the capabilities of doing so. Is there any way I can verify it's legality without a hacked Switch? If so, what resources do I have (if any) that I could try and use to *make* it legal, if it isn't already. Thank you in advance!