Max tier: I have some legendary troops, thats when I try to rank up it says that is on max tier, but..

Max tier: I have some legendary troops, thats when I try to rank up it says that is on max tier, but I see other players with the same troops with higher tier then me, I tryed to go from legendary to heroic, but some troops not allowed, but I see others with the same troops on heroic...

I don't understand, do I have to reach some game level to be able to rank up some of my troops to higher tier?

Also have some supreme troops on my journal, that doesnt show on my army list..... How does this work?!?!?