mtg sigarda commander deck EDH Tech - Sigarda, Font of Blessings - Holier Than Thou! Magic the Gathering: a Commander

Valley Rotcaller Valley Rotcaller ends games, even in Commander, as long as it can attack while you have the correct creature types

Your opponent has an ability to respond to your regeneration trigger

I can't say for sure

Archelos, Lagoon Mystic is a popular Gates commander since it lets them come into play untapped, though it also works in the 99

Gavin Verhey specifically stated multiple times in this announcement that a lot of the terms of these tiers fall under feel. It is technically very possible to build an incredibly powerful Commander deck that falls under the deck construction rules of the Exhibition Tier, but these decks are specifically weaker than the average Commander precon according to the second tier

Cosmic Spider-Mans also not all that interesting