FlashFlash is a static ability that functions in any zone from which you could play the card it’s on. “Flash” means “You may play this card any time you could cast an instant.”
Multiple instances of flash on the same object are redundant. (CR 702.8)
BackupBackup is a triggered ability. “Backup N” means “When this creature enters, put N +1/+1 counters on target creature. If that’s another creature, it also gains the non-backup abilities of this creature printed below this one until end of turn.” Cards with backup have one or more abilities printed after the backup ability. (Some cards with backup also have abilities printed before the backup ability.)
If a permanent enters the battlefield as a copy of a permanent with a backup ability or a token is created that is a copy of that permanent, the order of abilities printed on it is maintained.
Only abilities printed on the object with backup are granted by its backup ability. Any abilities gained by a permanent, whether due to a copy effect, an effect that grants an ability to a permanent, or an effect that creates a token with certain abilities, are not granted by a backup ability.
The abilities that a backup ability grants are determined as the ability is put on the stack. They won’t change if the permanent with backup loses any abilities after the ability is put on the stack but before it resolves. (CR 702.165) 1 (When this creature enters, 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 target creature. If that's another creature, it gains the following ability until end of turn.)
HexproofHexproof is a static ability.
“Hexproof” on a permanent means “This permanent can’t be the target of spells or abilities your opponents control.”
“Hexproof” on a player means “You can’t be the target of spells or abilities your opponents control.”
“Hexproof from [quality]” is a variant of the hexproof ability. “Hexproof from [quality]” on a permanent means “This permanent can’t be the target of [quality] spells your opponents control or abilities your opponents control from [quality] sources.” A “hexproof from [quality]” ability is a hexproof ability.
Any effect that causes an object to lose hexproof will cause an object to lose all “hexproof from [quality]” abilities. Any effect that allows a player to choose a creature with hexproof as a target as though it didn’t have hexproof will allow a player to choose a creature with a “hexproof from [quality]” ability. Any effect that looks for a card with hexproof will find a card with a “hexproof from [quality]” ability.
“Hexproof from [quality A] and from [quality B]” is shorthand for “hexproof from [quality A]” and “hexproof from [quality B]”; it behaves as two separate hexproof abilities.
“Hexproof from each [characteristic]” is shorthand for “hexproof from [quality A],” “hexproof from [quality B],” and so on for each possible quality the listed characteristic could have; it behaves as multiple separate hexproof abilities.
Multiple instances of the same hexproof ability on the same permanent or player are redundant. (CR 702.11)