I am a novice, and i read somewhere that when you meditate for somedays or months, your level of meditation will increase which i know. They said when it gets to a point, you reach the highest level of meditation and your spirit will leave your body and go to the third heaven, and sometimes the spirit comes back, sometimes it doesnt and then youll die. Is it true?
uh... i think you are speaking about astral projection. i don't thin meditation has levels like you'll suddenly hear 'congratulations you're now level 3' and be handed a piece of paper, but you can become better and go deeper into meditation.
what you are describing though sounds like astral projection. you go into a relax state to the point of almost falling asleep [make sure you don't] then your astral self [which you could think of as your spirit though its not] can leave your physical body. when its in the ethral [level between the astral and physical] you are able to travel all over the physical similar to a 'ghost'. when you finally project higher to the astral you are in a new parallel plane of existence.
this being said, no, you cannot die, or become lost when projecting. if anything happens to your body, it will immediately bring you back to the physical plane. [be it a knock at the door, your dog licking your face, or a spirit poking around] if you ever get 'lost' think of your room and you will instantly return.
This appears to be a strange mash-up of vague spirituality, astral projection and Christian cosmology. I don't believe Swiffs that you're entirely clear on what you're talking about; and I don't believe that the person who told you any of this is either.
"Third Heaven", in some Judeo-Christian beliefs, is a "section" of Heaven, where God is supposed to call his own, shall we say. I don't know where you got these ideas that you can meditate up to such a point where you can travel to it, and then die there? Terribly confusing ideas. Then again, the idea of Heaven itself confuses me, so there we go.
I recommend you try to find the source of whatever it was you read, or saw, that suggested this idea to you. It might help to re-read it, as you seem to be missing some information out potentially. Otherwise, I'd throw the idea out; it simply sounds like a mish-mash of ideas, that may or may not be true.