This is something I have not really looked into and I wonder if anyone know?

When it comes to sharing a review copy of an Android game to a review site etc before the game is released, that is as easy as just giving them the apk file. But is there any way to share an iOS game before it has been released in a good way?

After release you use promo codes. Prior to release, I believe it's possible with testflight. I think the reviewer would have to send you their device ID, and you add it to some permitted list.