After the activated ability resolves, the creature can’t be blocked this turn even if its power later increases to 3 or greater.

“Max speed — [ability]” means “As long as you have max speed, this object has [ability].” If the granted ability functions in a zone other than the battlefield, the max speed ability does too.

Start your engines! isn’t a triggered ability. Increasing your speed to 1 is something that happens as a state-based action as soon as you control a permanent with the ability. Notably, this includes gaining control of a permanent with the ability that another player controls.

Your speed doesn’t change until a spell or ability says so, such as the inherent triggered ability that cares about opponents losing life during your turn. Notably, losing control of permanents with start your engines! doesn’t affect your speed.

Hazoret’s activated ability must be used prior to declaring blockers to be effective. Activating it targeting a creature that has already been blocked will not cause that creature to become unblocked.

If an effect needs to know what a player’s speed is and that player doesn’t have a speed, their speed is considered 0.

Each player tracks their speed (or lack thereof) separately. Increasing your speed has no effect on whether another player has speed.

A player “has max speed” if their speed is 4.