If multiple sources deal damage to a creature with an enrage ability at the same time, most likely because multiple creatures blocked that creature, the enrage ability triggers only once.

If Polyraptor leaves the battlefield before its triggered ability resolves, most likely because it was dealt lethal damage, the token will still enter the battlefield as a copy of Polyraptor, using Polyraptor's copiable values from when it was last on the battlefield.

If lethal damage is dealt to a creature with an enrage ability, that ability triggers. The creature with that enrage ability leaves the battlefield before that ability resolves, so it won't be affected by the resolving ability.

The token won't copy counters or damage marked on Polyraptor, nor will it copy other effects that have changed Polyraptor's power, toughness, types, color, or so on. Normally, this means the token will simply be a Polyraptor. But if any copy effects have affected that Polyraptor, they're taken into account.

The token will have Polyraptor's ability. It will also be able to create copies of itself.