I'm also curious about the answer to this question. I am in the same situation.

I am residing in Turkey. But I came to Germany with the Erasmus program and I am living here until October 2022. My permanent residence is in Turkey. Right now, I will take advantage of the 50% discount of the interrail pass and buy a ticket where I can travel unlimited for a month. I will start my journey in Germany and finish it in Germany. Is this a problem? In the ticket information, it is said that there is only one right to go and one return to the country of residence. In this case, if I start from Germany, can I use it once in Germany? Do I have to start my trip from Turkey?

If you have a proof of residency for Portugal @Gracaugur /Germany @Cennet then you should be able to buy an Interrail pass. You have to be careful when you order your Interrail pass so that you get the correct country of residence. When you travel you will need to bring a proof of residence with you.

You can only use two travel days in your country of residence so you can only travel on 2 days in Portugal/Germany, to and from the border.

Hello! I have a similar problem, I am an Erasmus+ student I have a titre de séjour (résidence)  card  from France but it says temporaire (until the end of the year)  I am from Mexico,. I want to take advantage of the 50% but  I don't know if I am qualified for it. 

I would appreciate any answers :)