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)
CommanderA designated card for a Commander deck, governed by the command-zone, color-identity, and Commander rules. (CR 903) spells you
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) have
demonstrateDemonstrate is a triggered ability. “Demonstrate” means “When you cast this spell, you may copy it and you may choose new targets for the copy. If you copy the spell, choose an opponent. That player copies the spell and may choose new targets for that copy.” (CR 702.144). (When you
castTo cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect. A player may cast a spell if they have priority. See rule 601, “Casting Spells.”
To cast a card is to cast it as a spell. (CR 701.5) a
commanderA designated card for a Commander deck, governed by the command-zone, color-identity, and Commander rules. (CR 903) spell, you may copy it. If you do, choose an opponent to also copy it. The copies become tokens.)
The "legend rule" doesn't apply to commanders you control.