Wormfang Manta + Flickerform + Doorkeeper Thrull

Decks

How it works

Activate Flickerform by paying , exiling Wormfang Manta and all Auras attached to it.
When Wormfang Manta leaves the battlefield, its second ability triggers, causing you to take an extra turn after this one.
At the beginning of your end step, Flickerform triggers, returning Wormfang Manta from exile to the battlefield, and then returning all Auras that were attached to Wormfang Manta from exile to the battlefield attached to Wormfang Manta.
Wormfang Manta's first ability does not trigger due to Doorkeeper Thrull.
Repeat each turn.

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

1–2 · Exhibition & Core

Spellbook classifies this as Ruthless — not for these brackets.

3 · Upgraded

Spellbook classifies this as Ruthless — not for these brackets.

4–5 · Optimized & cEDH

All combos are allowed.