Does Temporal Breach reset all modifiers and empowered status of the unit?

Yes, Temporal Breach resets both. The unit is banished (leaves the board for a Non-Board Zone), then replayed as a new object — it enters play with none of its previous baggage.

• All modifiers (stat buffs, granted keywords, damage, etc.): Cleared by Rule 110 — any zone change to/from a Non-Board Zone wipes all Temporary Modifications. The replayed unit is also a fresh game object per FAQ #6697, so it doesn't retain previous buffs or effects.
• Empowered status: Explicitly lost. Per the Vendetta rules, the Empowered status "lasts indefinitely until the card leaves the board or is disempowered." Banishment is leaving the board, so the status is removed. The replayed unit enters without it and would need to be Empowered again from scratch.