Two Floors, One Difficulty Curve
The Outer Gates is the classroom and The Heavenly Courtyard is the exam. The Gates hand you every tool one at a time; the Courtyard assumes you carry healing items, upgraded chips and the habit of reading telegraphs. The comparison table on the region comparison page breaks the differences down number by number.
You can return to Floor 1 at any time — the hub laboratory still buys Floor 2 drops at full value, and the fast-trip gate opens both ways once you have the Key.