The value of X is determined only as you perform the third mode while Inscription of Insight is resolving. Once that happens, the value of X won't change even if the number of cards in the player's hand changes.

If any targets become illegal, the other targets will still be affected as appropriate. If any targets are chosen and every target becomes illegal, Inscription of Insight doesn't resolve. You won't scry 2 or draw two cards if the middle mode was chosen.

If you kick Inscription of Insight, you can't choose any one mode more than once.

If more than one mode is chosen, perform them in the order written. Nothing can happen in between, however, and no player may choose to take actions. Any abilities that trigger will be put onto the stack after the spell has finished resolving.

If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.

If a spell's kicker cost was paid, the spell is "kicked."

If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.

The kicker ability doesn't let you pay a kicker cost more than once.

If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.

To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.