Unity 5 only works for lecture 38 then revert back to Unity 4

After lecture 38 I kept using unity 5 but when I got to lecture 89 it became impossible to do so then I tried to open the project in unity 4 and revert and it deleted my scripts and assets so now I am just watching the videos with a blank project until the next game. There was a popup in lecture 38 saying keep using unity 4 after this lecture now that I go back and look at it but perhaps a few different reminders including the narrator stating it would help people in the future not make this same mistake that I did.

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