Answer
Hong Taiji's significant transformations in 1635 and 1636 involved altering the empire's name from "Later Jin" to "Qing" and implementing a strategic shift in ethnic identity. By officially declaring the Manchus as the ruling ethnicity and adopting the "Qing" moniker, Hong Taiji aimed to consolidate power, unify diverse ethnic groups under a common identity, and legitimize his dynasty's rule over China.