Rapid Strike Urshifu VMAX

When using Mega Lopunny ex's "Gale Thrust" attack, what counts as "moving to the Active Spot this turn"?

Your turn starts when you draw a card. If Mega Lopunny ex moved to the Active Spot prior to that, it is not during your turn. For example, if your opponent KO'd your Active at the end of their turn, moving Mega Lopunny ex to the Active Spot at that time is during their turn. Or if your Active was KO'd by Poison during Pokemon Checkup between turns, that is also not during your turn. And finally, if Buneary moved to the Active Spot during your turn and then evolved into Mega Lopunny ex, that would not count because it was Buneary when it moved to the Active Spot.

If I use Keldeo ex's "Gale Thrust" attack after I move it up to replace a Pokemon that was KO'd by an opponent's attack, does it do the extra 90 damage?

No, Keldeo ex was moved to the Active Spot during the opponent's turn, not during "this turn".