Fighter Class

• WWizards of the Coast2021-07-23
  Official Ruling
  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.
• WWizards of the Coast2021-07-23
  Official Ruling
  Gaining a level is a normal activated ability. It uses the stack and can be responded to.
• WWizards of the Coast2021-07-23
  Official Ruling
  You can multiclass or even control multiple Class enchantments of the same class. Each Class permanent tracks its own level separately.
• WWizards of the Coast2021-07-23
  Official Ruling
  The discount to equip abilities applies only to generic mana requirements. If you control multiple Fighter Classes that are level 2 or higher, equip abilities cost less for each one. This can't make an ability cost less than .
• WWizards of the Coast2021-07-23
  Official Ruling
  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.
• WWizards of the Coast2021-07-23
  Official Ruling
  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.
• WWizards of the Coast2021-07-23
  Official Ruling
  Each Class has five abilities. The three in the major sections of its text box are class abilities. Class abilities can be static, activated, or triggered abilities. The other two are level abilities, one activated ability to advance the Class to level 2 and another to advance the Class to level 3.
• WWizards of the Coast2021-07-23
  Official Ruling
  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.
• WWizards of the Coast2021-07-23
  Official Ruling
  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.
• WWizards of the Coast2021-07-23
  Official Ruling
  Gaining a level won't remove abilities that a Class had at a previous level.

Rulings via Scryfall