how can I get a trial license for v3.5, I download the license from the website and only sents for v4.1. I try to added it and does not recognize it.

Any special reason that you want v3.5? v4 is the official one, so it is the version available for trial. Anyway you can open v3.5 projects from LLBLGen v4 and migrate them. If you purchase v4, you can access all v3.x and v2.x downloads from the customer area.