FlyingFlying is an evasion ability.
A creature with flying can’t be blocked except by creatures with flying and/or reach. A creature with flying can block a creature with or without flying. (See rule 509, “Declare Blockers Step,” and rule 702.17, “Reach.”)
Multiple instances of flying on the same creature are redundant. (CR 702.9)
DethroneDethrone is a triggered ability. “Dethrone” means “Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on this creature.”
If a creature has multiple instances of dethrone, each triggers separately. (CR 702.105) (Whenever this creature attacks the player with the most life or tied for most life, 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.)
Whenever this creature attacks for the first time each turn, if it's attacking the player with the most life or tied for most life,
untapTo untap a permanent, rotate it back to the upright position from a sideways position. Only tapped permanents can be untapped. (CR 701.26) all attacking creatures. After this phase, there is an additional combat phase.