If one target of an escalate spell becomes illegal, the other targets will still be affected. If all of the targets become illegal, the spell won’t resolve.

You can’t choose any one mode multiple times.

Additional costs don’t affect a spell’s mana value.

You choose all of your modes at once. You can’t wait to perform one mode’s actions and then decide to choose more modes.

Effects that reduce the cost of spells reduce the total cost, including any escalate costs added.

Untapping an attacking creature doesn’t cause it to be removed from combat.

If two of the chosen modes of an escalate spell target a creature, you may choose the same creature for each mode’s target, or choose different creatures. The same is true if the chosen modes target a player (or opponent).

The targeted opponent chooses which of their attacking creatures to sacrifice, not you.

If an effect allows you to cast a spell that has escalate without paying its mana cost, you pay escalate costs for that spell if you choose more than one mode.