I'm at the part where the snakes head and tail come out on year 2 I've..

Hi! It's hard to answer your question exactly because I am unsure what you mean by "right" when you say you cannot jump right, but I can try to offer some help! You are correct in saying you must use reducto on the tail of the snake to make it move, however on certain areas you cannot cast reducto and you must jump nearby where you will see the painting of the snake for Harry to hiss at, and that will call the snake away from it's current location towards you, and so if you jump away quickly you may access where it was recently occupying. Also, sometimes you have to be standing just right on the platform to be able to jump. While being careful not to fall, try wiggling around a bit while on the platform! Last but not least, there is a portion where there are three platforms laid side-by-side, with the middle one able to be raised in order to grab coins. These platforms can actually be walked straight across, and from there you can jump to the right. Hope this helps! (: