Hello!
You may refer to this forum post to hopefully gain some insight to your questions: http://forum.playrohan.com/forum/sho...#axzz5WCUxQCNV
1. Yes, it is possible to transcend trinity weapons. To do this, the weapon needs to reach max level which is 140. There will be a total of 3 slots.
2/3. You can’t transmute a weapon that is already transcended into trinity weapons. It has to be a normal/upgraded weapon that is not transcended.
4. To some certain degree it is, but it really all depends on luck. Just don’t forget to use preservation stones!