Hello, I have a 14th Thief and I was told by GM that I have access to passages at 4th Circle.
But I am not able to use the one from Crossing to Leth.

Is there other requirements that I have to meet ?

made it to 30th and passages still don't work, maybe it's another thing they took way from F2P thieves.

I had access to the 5th passage to leth before I even had the swimming skill to make it through. You may have to ask the crossing guild leader about magic before you'll learn it? I'm not sure how that will work with the new khri, but it's worth a shot. From an archive of drsecrets: "To learn these abilities, you must ask the respective guild leader about magic." and "6 Passages Crossing You will now see marks in room descriptions that lead to thief-only passageways."