Dimensions in debug world

Entering to the nether portal block will make you go to a nether version of debug world (Pic 1), but if you use the nether portal again youll spawn somewhere unkown (Pic 2).

If entering the end portal, you'll access an End version of debug world, the enderdragon is there too (pic 3, sorry for the resource pack). Some chunks make most blocks there invisible (pic 4-5).