Blue Sun's Twilight + Dockside Extortionist + Chandra, Hope's Beacon + Displacer Kitten + Mnemonic Wall

Banned

Decks

How it works

Cast Blue Sun's Twilight by paying , targeting Mnemonic Wall.
Chandra and Displacer Kitten trigger.
Resolve the Displacer Kitten trigger, blinking Chandra.
Resolve the Chandra trigger, creating a copy of Blue Sun's Twilight, targeting Dockside Extortionist.
Resolve the copy of Blue Sun's Twilight, creating a token copy of Dockside Extortionist.
The Dockside Extortionist token enters the battlefield, creating at least eight Treasure tokens.
Resolve the original Blue Sun's Twilight from step 1, creating a token copy of Mnemonic Wall.
The Mnemonic Wall token enters the battlefield, returning Blue Sun's Twilight from your graveyard to your hand.
Activate seven Treasure tokens by tapping and sacrificing them, adding .
Activate Chandra's third loyalty ability by removing four loyalty counters from it, dealing four damage to up to two targets.
Repeat.
Once you have infinite mana, you may instead target Mnemonic Wall and any other creature to get infinite copies of any creature on the battlefield.

In which brackets is this combo allowed, per Spellbook's Banned tier?

1–2 · Exhibition & Core

Spellbook classifies this as Banned — not for these brackets.

3 · Upgraded

Spellbook classifies this as Banned — not for these brackets.

4–5 · Optimized & cEDH

Spellbook classifies this as Banned — not for these brackets.