They're not removed if the creature regenerates or the turn ends
The Dominion Bracelet isn't too great of a card, and is more of a gimmick card than anything
However, you must still follow any other timing restrictions, such as "Cast [this spell] only during combat." (8/23/2016) You can't pay any alternative costs the card has
I imagine the play pattern will be to cast Seek Thrills first from the command zone, and then once Beluna ends up back in the command zone, youre already at the five mana youd need to just cast Beluna Grandsquall
The worst part: even though Dual Casting is a tap ability, you can usually put the aura on a creature which was already in play so assuming the spell you want to copy is an instant, you can go from innocuous boardstate to comboing off in the same turn for just four or five mana
That can soften the paper fibers, create banding in the art, and change the way sheets curl as they dry