The token created by Jace's triggered ability doesn't have the legendary supertype and has a starting loyalty of 1 rather than 4. If another object becomes a copy of the token, that copy also won't be legendary and will have a starting loyalty of 1.

If the mana value of the drawn card is greater than Jace's loyalty, you remove all loyalty counters from him. He'll be put into your graveyard as a state-based action before you can take any actions.

If the card draw from Jace's last ability is modified by a replacement effect, you don't reveal any card, even if the draw was replaced by one or more card draws. No loyalty counters will be removed from Jace in that case.

You can control one legendary Jace, Mirror Mage in addition to any number of nonlegendary copies of Jace, Mirror Mage.

The token from Jace's triggered ability copies exactly what is printed on Jace and nothing else. It doesn't copy how many counters are on him, or any non-copy effects that have changed his color or types, and so on. It enters the battlefield with one loyalty counter. You can activate one loyalty ability of each of the Jaces this turn.

While resolving Jace's last ability, you must reveal the card before it's mixed with the other cards in your hand.

If a card in a player's hand has {X} in its mana cost, X is considered to be 0.

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.

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

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.

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

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