Is it possible to get on top of the nether in survival mode in Minecraft?
There are many ways to do it, but they all are technically glitches. The basic methods involve clipping through blocked by use of ender pearls, or hit box collision, to eject you onto the other side of the nether ceiling.
There are many videos explaining how to do it, and some even can explain how to remove the bedrock. None of these are technically cheating however, they are simply exploiting the physics of the game.