When I was playing jj2 TSF I've made some lvl. When I got jj2 1.23 version and tried to open this file in 1.23's JSC to corret it, I saw the message: "Unsupprted level file version 2.03, this lvl cannot be loaded". The same situation was when I try to open this level in the game. How can I change the version of this file to run it on 1.23 game or in JSC??
PLEASE TRY TO HELP ME, as.

you CANT use a TSF level in 1.23.
other way around can. (use 1.23 levels in TSF)
its very difficult (but possible) to change a TSF level into an 1.23 level, but most likely you arent gonna get it to work.

(it involves replacing part of the level file (the "header") with teh smae part of an 1.23 file, from a level with exactly the same *filesize* (so not teh same number of tiles.)