Can you only get Danse's perk after blind betrayal?

Yes, Blind Betrayal is a requirement, as it's almost like his personal quest.

I wanted to ask the same question. Can somebody help a little bit more and tell do I have to build that teleporter with BOS faction to get "Blind betrayal" quest? What if I build it with the Minutmen, will it lock for me the Blind betrayal?

No, you don't need to build the teleporter with the BoS, I build it with the Minutemen, and all you have to do is to ask Sturges for the data and give it to the BoS to anolyze.

Great thanks ! Now I feel much better knowing I still can do this quest. I already started to think that I`ve lost my chance to learn the trueth about Danse.

No. It's fine. That's what I did.

Thank you. I decided to do all possible side quests before I choose the side, so I can make a save and try all possible endings without loosing any progress in other quests. But I already have built that ...teleporter with the Minutemen so I just was worrying that I locked Danse`s quest by it.