Have you tried "free mode" and "fast mode"?
First write this in chat (press T):
Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.
Then this:
Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.
Of course, replace "yourusername" with your in-game name (in single player, you are "singleplayer")
And then press J to toggle "fast mode" (press & hold E to run), and K to toggle "free mode".
In free mode, W-S-A-D are your normal movement keys, while SPACE is "Up", and SHIFT is "Down" (depending on your configuration E may be "Down"). Also while on free mode, J toggles moving fast or slow (don't need to hold E).
In free mode, there is no gravity, and you can pass through any solid block. If you are accustomed to play First Person Shooters (Quake, Half-Life, etc), you can consider this "noclip".
Is this what you meant?