Unstable Footing's effect causes damage from all sources to be unpreventable, not just damage from Unstable Footing itself.

If damage can't be prevented, static abilities that prevent damage (including protection abilities) don't do so. If they have additional effects that don't depend on the amount of damage prevented, those additional effects will still work. Such effects are applied only once per source of damage.

If Unstable Footing is kicked and the targeted player is an illegal target by the time it resolves, the entire spell doesn't resolve. Damage can still be prevented.

Effects that replace or redirect damage without using the word "prevent" are not affected by Unstable Footing.

If a creature is dealt lethal damage, it can still regenerate. If it does, the damage marked on it will be removed from it.

If damage can't be prevented, damage prevention shields don't have any effect. If a prevention effect has an additional effect, the additional effect will still work (if possible). Spells that create prevention effects can still be cast, and abilities that create prevention effects can still be activated.

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.

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 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."