can i still install old version of unity?like 2.6

can i uninstall unity version 3 which i registered online and install an older version of unity?i recently been viewing unity tutorials and it uses 2.6. Tried making it in the new version but there are a lot of differences. some won't work or atleast i don't know how to make it work.

Hope you can help me out..

Yes, you can do taht. I recommand contacting support@unity3d.com for help. You will need to inform Unity team that you will uninstall Unity from your machine. (Since the license key can be used only twice)

You can pick which old version of unity you want to install from here:

https://unity3d.com/unity/download/archive