These bugs are almost impossible to do in mobile (although possible).
There is one that involves changing the cosmetics to cause a visual bug but can be done via mobile (not displayed in the video). There is also one that allowed to gain infinite XP via quest claims only possible via mobile as far as I have tried.
The main bug here is done by maximizing your fishing line bar to yellow and going to the cardinal direction you want to go while being nearby water and then quickly reloading your page (clicking the refresh tab button or Ctrl+r or CMD+r) and waiting for 3 to 15 seconds before cancelling the refresh tab action. Otherwise, if you wait longer the game will log you out. Then by cancelling your fishing line and maximizing it again until the bar is yellow–you stop holding the fishing line and rapidly move towards any direction and as you will see the game will refresh your position to the real one. I believe this bug happens because of the lag caused while refreshing your tab which builds up to the direction you travelled to.
1. go to the bottom of the dock (down)
2. hold your fishing line and maximize it turns from green until it’s yellow
3. release it and immediately after move and *hold* upwards and only upwards and following that immediately after press Ctrl+r to reload
4. wait a few seconds
5. press cancel to not reload
6. hold your fishing line until it’s fully yellow like before and release your fishing line towards close water but as soon as you do this move to any direction
there is no room for mistakes in timing
(If you do this right you will see the bug worked for using the up arrow key only later if you get the hang of it you can do this in any direction and move to different places if you repeat steps 1 to 5 twice)