Default [Q] Upgraded to KitKat, its not possible to go back to JellyBean??

From what ive read and understand, if you try to flash to 4.3 after already having upgraded to 4.4.2, you will brick your phone or it just wont work? Is this true or not, please help! IF you can flash to a previous OS, can anyone post a link on how to do it the right way or explain how to do this, preaze?