Is Tengen Uzui Alive?

Not to mention Tengen didn't die luckily and was saved by our strongest protagonist "Tanjirou Kamado" by the flame god breathing techniques.

What happened UZUI Tengen?

Tengen is one of the only known Demon Slayer and Hashira to retire due to being permanently disabled instead of death or age, the other being Jigoro Kuwajima.

Which Hashira are dead?

Chapter 204 also confirms the deaths that occurred during the final arc with several members of the Hashira losing their lives including Shinobu Kocho, Mitsuri Kanroji, Obanai Iguro, Gyomei Himejima, and Muichiro Tokito.