I want to join a dermatological clinical trial

Hey guys. So when I was a child I suffered from scalp psoriasis (or so that's what my doctor said). But I immediately treated it with coal tar shampoo and for over a decade now I haven't had symptoms. I just want to know if I have areas of scalp which are free of symptoms does it mean my skin is cycling monthly like it's supposed to? If you have certain areas of the scalp symptom free but others with the red flakes does it mean the autoimmune action is only happening locally there? I understand that the underlying process could still be occurring without symptoms as well. I guess the question is, if you go into a remissive state, can your skin go back to cycling normally and thus cell signalling/healing ect is normal? Can you have one area of the skin with symptoms cycling every 3/4 days and other areas of the scalp on a normal cycle? It's really hard to find these answers anywhere and are quite important to me. I was also wondering if It is within my rights to demand a biopsy from the GP even if currently I have no symptoms? Would a biopsy of uneffected skin even show psoriasis? I feel like I need to know if I am truly suffering from an autoimmune disease or could the problem have been sub derm ect. If I remember rightly the flakes were moist and sticky and I could pick them but again it is hard to judge since I was young. Thanks for reading and sorry for all the questions guys!