Breath of Fury + Living Hive + Concordant Crossroads

Decks

How it works

Deal combat damage to an opponent using Living Hive and the creature with Breath of Fury attached.
Breath of Fury and Living Hive trigger.
Resolve the Living Hive trigger, creating six 1/1 Insect creature tokens.
Resolve the Breath of Fury trigger, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to an Insect token, untap all creatures you control and get an additional combat phase after this one.
Repeat each combat phase.
Deal combat damage using the creature that has Breath of Fury attached and Living Hive, triggering Breath of Fury and Living Hive.
Resolve the Living Hive trigger, creating at least one creature token.
Resolve the Breath of Fury trigger, causing you to sacrifice the creature it is attached to, then attach Breath of Fury to a creature 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.