Hello. When I enter the 4-2 Warp zone, only the world 5 pipe appears. Does anyone know why?

Wrong warp zone

You probably did the same thing as 1-2 and went over the top till the end. That warp zone only has the world 5 pipe. You need to climb a hidden vine right after the moving platforms to get to the warp zone with world 6, 7, and 8 pipes.

Yeah, there are 2 differents warp zones in 4-2
You should look a video to know where is it
If you go up and continue with only world 5, or an extreme glitch happend or just you use big mario with the low mushroom floors to just go much to the rigth of the screen and make a wrong warp glitch that make you to go to world 5 (in all case I dont know if you go to world 5 doing that but maybe)