FAQ for importing own vihicle (Geneva)

Hi everyone!
I'm going to Geneva next month for a one year MBA program.
I decided to go on my own car. The car has Belorussian plates. And that's why I have some questions about this process and legacy.

The main question is how long can I stay in Switzerland with my car without any registration, tax fees and problems with Police?

I called to the Road Police service and they told me that as I'm going there like a student, I can make the 15.30 authorization form for all my studies period and will have no problems. But I don't know where and how can I do it.
I'm planning to leave the country every 3 month and maybe in these reason I can just stay in Geneva without any registrations.

It would be very helpful for me if anybody knows the aspects of this problem.
Or can write FAQ about this 15.30 registration process.