Okay guys , this is an amazing exploit to have your character multiclassed..Tested and works on Lineage2J Interlude Servers..
What you need is your server to have delevel..
You have to xp your character to lvl 40 , and take your skills ... of the class you have choosen
Now you can have a bot , and start killing this char till he got 20 lvl.. , unfortunatelly you will be available to take again class from the class manager and you are gonna have both skillzZ..
What we have here?A MultiClass character !! So simple , withought any problemzZ with clas changer..