You may tap or untap target creature. Then that creature's controller may pay


. If the player does, they may copy this spell and may choose a new target for that copy.
The spell copy has all the text and can result in itself being copied.
The decision to tap or untap is made on resolution of the spell (and of each copy).
Paying to make Chain Stasis continue is done as part of the resolution of the spell.
The player putting the copy spell on the stack controls that spell.
The copy is a spell, so it can be targeted by other spells and abilities that target a spell.