Let's talk about the corresponding shortcut keys first:

Full screen mode host +F

Seamless mode host +L

Auto zoom mode host +C

Where Host (default) is the Ctrl key on the right.

You can switch the corresponding mode through the corresponding shortcut key above, and press the corresponding shortcut key again to exit from this mode to the window mode normally.

So, you've entered a certain mode,

Try it alone:

Right Ctrl+F, right Ctrl+L, right Ctrl+C

There must be a key to help you get out of normal mode.

In addition, regarding the use of virtualbox, if you don't know, you can refer to my summary:

Crifan recommends virtual machine software VirtualBox.

I don't want to post the address here. Please Google the title yourself and you will find the post address. )