Learn English – “They are never” or “They never”

Your two phrases are correct and often used

He told be to buy the red car, which I did.
Mom wanted me to wash the dishes, which I did.

She is hungry, but I'm not.
They are from America, but I'm not.

Did you change any thing in file

This sentence is grammatically correct

Are you change anything in file

This sentence is grammatically incorrect. Instead one should use the following sentence Are you changing anything in file

The difference between both sentences is that in first you are talking about past while in second you are talking about present.