Rhino 7 installation

I have been using Rhino 6 student version. I would like to install Rhino 7.
But I have found only “WIP - Work in Progress” version.

  1. Is there only WIP version?
  2. How can I install “add-in” of Rhino 7 in Revit?

Thanks!

Yes. Rhino 7 is under development, not released yet. You must have a paid license for Rhino 6 to use Rhino 7 Work-in-Progress (WIP) because it uses your Rhino 6 license.
Each WIP release is good for 45 days, then you must download and install a newer version (usually released once a week, but not always) to continue with your testing.
McNeel does this to receive user bug reports and feedback on new features and the general direction of development they are pursuing.

You will need to wait for someone more qualified than me to answer your 2nd question.