What if papers were not signed legally? What if you are not told what you are arrested right away?

Ok I know two questions but I need help. We live in Wyoming and I know that procedures are done differently in every state but here goes. My fiance was taken in for questioning and it was taped but I was recently told that if he actually confessed to what they are saying he confessed to he should have signed a piece of paper saying that he confessed-is that true? Also he did not signed anything waiving his rights to his preliminary hearing--is that right? What could happen with all this? I was also arrested and all he told me was that I had a warrant and that was it and then he waited until we was two blocks away from my house to tell me what I was arrested for. Can they do that? There is alot more going on but can't go into details right now.