Fighter Class

If the last triggered ability triggers more than once in the same combat, a single creature may be required to block more than one creature. As long as it doesn't have an ability that would allow that, its controller choose which attacking creature it blocks.

You can't activate the first level ability of a Class unless that Class is level 1. Similarly, you can't activate the second level ability of a Class unless that Class is level 2.

Gaining a level won't remove abilities that a Class had at a previous level.

Each Class starts with only the first of three class abilities. As the first level ability resolves, the Class becomes level 2 and gains the second class ability. As the second level ability resolves, the Class becomes level 3 and gains the third class ability.

For the last triggered ability, if the target creature is tapped or is affected by a spell or ability that says it can't block, then it doesn't block. If there's a cost associated with having that creature block, its controller isn't forced to pay that cost, so it doesn't have to block in that case either.

Some Class cards have an effect that increases when more are under your control. For example, if you have multiple Barbarian Class cards, you roll that many additional dice and ignore that many of the lowest rolls.