My cursor has changed to a white circle with a white cross in the middle although my screen capture doesn’t show the cross. I can’t revert to the usual arrow cursor.
Googling suggested I had circle selection switched on, initiated via C, from which right-mouse or esc would exit. However, I don’t think it’s circle selection as those ways to exit the situation don’t work.
On closing the blend file and opening another one, the cursor reverts to an arrow.
You have done what i kept doing by trying to go into fly mode (Which is now control and tilde not F), After that i press W to move the camera forward which of course didnt work because they changed the fly mode shortcut.
What W does do though is change the selection method in the top left there to a circle and other methods. Just keep pressing W until you get back to the box selection as before