In American English, "revert" never means "respond" or "reply." That is an Indian English usage. We don't use it that way in the United States. (I don't know about this usage in British English.) "Revert" means "to return to a former habit, practice, belief, condition, etc." - https://www.dictionary.com/browse/revert Revert is often used with "back" but not always. Examples: 1a. She reverted to her old bad habits when she returned to her hometown. 1b. She reverted back to her old bad habits when she returned to her hometown. 2a. Scientists can make cells revert to an earlier developmental stage by manipulating their DNA. 2b. Scientists can make cells revert back to an earlier developmental stage by manipulating their DNA. Both versions (a) and (b) are correct. Without "back" is slightly more old-fashioned and formal. With "back" is more common and informal.

Edited* “Revert” is equal to “get back” when it is being used in place of respond or reply. Ex: “I will get back to you” or “I will revert to you” It is also commonly used in place of “change” in “change back” for example: “Cinderella’s dress will revert at midnight.” Or “Cinderella’s dress will change back at midnight.” Saying “revert back” would be similar to saying “get back back”

Yes, it means to turn back (to something prior). Example: When I can’t think of the word I want to use in French, I revert back to English.

Revert is now very commonly used in software development. Changes may get reverted if they are incompatible, have bugs, or have unintended side-effects.