First strikeFirst strike is a static ability that modifies the rules for the combat damage step. (See rule 510, “Combat Damage Step.”)
If at least one attacking or blocking creature has first strike or double strike (see rule 702.4) as the combat damage step begins, the only creatures that assign combat damage in that step are those with first strike or double strike. After that step, instead of proceeding to the end of combat step, the phase gets a second combat damage step. The only creatures that assign combat damage in that step are the remaining attackers and blockers that had neither first strike nor double strike as the first combat damage step began, as well as the remaining attackers and blockers that currently have double strike. After that step, the phase proceeds to the end of combat step.
Giving first strike to a creature without it after combat damage has already been dealt in the first combat damage step won’t preclude that creature from assigning combat damage in the second combat damage step. Removing first strike from a creature after it has already dealt combat damage in the first combat damage step won’t allow it to also assign combat damage in the second combat damage step (unless the creature has double strike).
Multiple instances of first strike on the same creature are redundant. (CR 702.7)
RenownRenown is a triggered ability. “Renown N” means “When this creature deals combat damage to a player, if it isn’t renowned, put N +1/+1 counters on it and it becomes renowned.”
Renowned is a designation that has no rules meaning other than to act as a marker that the renown ability and other spells and abilities can identify. Only permanents can be or become renowned. Once a permanent becomes renowned, it stays renowned until it leaves the battlefield. Renowned is neither an ability nor part of the permanent’s copiable values.
If a creature has multiple instances of renown, each triggers separately. The first such ability to resolve will cause the creature to become renowned, and subsequent abilities will have no effect. (See rule 603.4) (CR 702.112) 1 (When this creature deals combat damage to a player, if it isn't
renownedA designation a creature gains from renown until it leaves the battlefield. (CR 702.107), put a +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on it and it becomes
renownedA designation a creature gains from renown until it leaves the battlefield. (CR 702.107).)
Whenever this creature attacks, if it's
renownedA designation a creature gains from renown until it leaves the battlefield. (CR 702.107), other attacking creatures you control get +1/+1 until end of turn.