Doom's Time Platform + Shivan Sand-Mage + Capture of Jingzhou + Thassa, Deep-Dwelling

How it works

You control a creature that can attack and that cannot be blocked or killed by an opponent.

Declare any creature as an attacker. When you do, Doom's Time Platform triggers, exiling Capture of Jingzhou from your graveyard with two time counters on it.
Blink Shivan Sand-Mage using Thassa.
When Shivan Sand-Mage enters, it triggers, removing two time counters from Capture of Jingzhou.
Capture of Jingzhou's suspend ability triggers, causing you to cast it without paying its mana cost.
Resolve Capture of Jingzhou, causing you to take an extra turn after this one.
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.