Aya of Alexandria + Breath of Fury + Concordant Crossroads + Encroaching Mycosynth

How it works

Deal combat damage using the creature that has Breath of Fury attached.
Breath of Fury and Aya of Alexandria trigger.
Resolve the Aya of Alexandria trigger, creating a 1/1 Assassin creature token.
Resolve the Breath of Fury trigger, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to the Assassin token, then causing you to untap all creatures you control and to get an additional combat phase after this one.
Repeat each combat phase.

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

1–2 · Exhibition & Core

Allowed in this bracket.

3 · Upgraded

Allowed in this bracket.

4–5 · Optimized & cEDH

All combos are allowed.