Quick Question on Unique Summons

[DonCorazon]

What happens if say, you cast Queen of Elemental Air, and all the queens have been summoned? Will the game let you attempt to cast and it then fails, effectively wasting a caster's turn? Do you lose your gems?

Finally, for the vets, about what turn do you expect most unique summons will have been cast?

I am just learning endgame strategies on some of my first MP game, (prolly a little too late )

Thanks!