If Haktos can't attack for any reason (such as being tapped or having come under that player's control that turn), then it doesn't attack. If there's a cost associated with having it attack, you aren't forced to pay that cost, so it doesn't have to attack in that case either.

Haktos has protection from each possible mana value other than the chosen value, not just protection from the two options that weren't randomly chosen.

For spells with {X} in their mana costs, use the value chosen for X to determine the spell's mana value. If a card or permanent in any other zone has {X} in its mana cost, X is considered to be 0.

The mana value of a token that isn't a copy of another object is 0. A token that is a copy of another object has the same mana value as that object.

A number is chosen randomly for Haktos before it enters the battlefield. There's no point at which players can target it before it has gained the appropriate protection abilities.

If Haktos somehow has no choice made for its ability, its last ability grants it no protection abilities.