Can I move units from different battlefields with Emperors Divide?

No. Emperor's Divide can only move units from a single battlefield. The card text says "at a battlefield" (singular), so you must choose one battlefield and move units only from that location.

If it were intended to affect multiple battlefields, it would use plural wording like "at battlefields." Units moved by Emperor's Divide retain their current state (Ready or Exhausted) when they arrive at your base.