How to update your roblox without the app store

Technically, this is not allowed legally, due to the guidelines that both Apple and Android try to follow by:

Apps should be self-contained in their bundles, and may not read or write data outside the designated container area, nor may they download, install, or execute code which introduces or changes features or functionality of the app, including other apps.

I found this quote from Apple’s App Development Guidelines, and Googles has nearly the same guidelines as well.