Multiple finality counters on a single permanent are redundant.

If a creature that dies leaves the graveyard before Meathook Massacre II's second or third ability (as appropriate) resolves, that creature won't return to the battlefield regardless of whether or not life was paid.

When a token creature dies, Meathook Massacre II's second or third ability (as appropriate) will trigger. The appropriate player has the option to pay 3 life, but regardless of their choice, the token won't return to the battlefield.

Finality counters work on any permanent, not only creatures. If a permanent with a finality counter on it would be put into a graveyard from the battlefield, exile it instead.

Finality counters don't stop permanents from going to zones other than the graveyard from the battlefield. For example, if a permanent with a finality counter on it would be put into its owner's hand from the battlefield, it does so normally.

Finality counters aren't keyword counters, and a finality counter doesn't give any abilities to the permanent it's on. If that permanent loses its abilities and then would go to a graveyard, it will still be exiled instead.