Hofri Ghostforge's last ability is linked to the ability it grants the Spirit token. If a replacement effect causes you to create more than one Spirit token with this effect, they will all have that ability, and the exiled card will be returned to the graveyard if any of them leaves the battlefield.

If another creature enters the battlefield as a copy of the Spirit token or another effect creates a copy of the Spirit token, it will have the triggered ability granted by Hofri, but will not be linked to Hofri's ability and will not return the card to the graveyard when it leaves the battlefield.

Each Spirit token you create refers only to the card you exile during the resolution of the ability that created that token. When it leaves the battlefield, you return only that card to your graveyard, not any other card exiled by Hofri.

If you can't exile the card, perhaps because another effect moved the card before the triggered ability started resolving, you won't create a token.

The copy uses the copiable values of the creature as it last existed on the battlefield before it died, not as it existed in the graveyard before it was exiled.

The token copies exactly what was printed on the original creature and nothing else (unless the creature was copying something else; see below). It doesn't copy whether that creature was tapped or untapped, whether it had any counters on it or Auras or Equipment attached to it, or any non-copy effects that changed its power, toughness, types, color, or so on.

If the copied creature was copying something else, then the token enters the battlefield as whatever that creature copied.

Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any "As [this creature] enters the battlefield" or "[This creature] enters the battlefield with" abilities of the creature will also work.