Are Chautha and Uthala the same ceremony?

No, Chautha and Uthala are different ceremonies on different days with different purposes. Chautha is the community gathering on Day 4 — it is a social ceremony of collective mourning where relatives and neighbours acknowledge the death together. Uthala (also called Daswan or tenth-day ceremony) takes place on Days 10 to 12 and involves formal purification: the chief mourner and family members bathe outside the house, discard the clothes worn throughout mourning, and the men often undergo Mundan (head shaving). The Uthala also includes the critical tenth Pinda offering — the one that feeds the soul that has just become capable of experiencing hunger for the first time, according to the Garuda Purana Preta Kalpa.