Make sure that you always change your birthday, even if it’s a wrong one, to 13 years of age or older to be able to change it at a later date. How to change your age on Roblox account (PC desktop)?

Steps for altering your avatar’s appearance in every Roblox experience, from adding and removing items to changing your skin ...

To change your Roblox username login to your account and go to the settings section. In a browser this is represented by the gear icon in the upper-right corner.