Sorry for the newbie-question, but, is it possible to snapshot state of virtual machine with all processes inside?
For example, state of running single-player game. I want to pause the game process, then move to friend's computer and continue playing without interruptions.
Depends on how you're defining "snapshot".
If you snapshot a system, it will take the state of all processes for that singular system. If your game has any external dependencies, such as a network based file system or services running from a different systems, those will not be referenced.
Of note, you'll need to move the entire VM from your system to your friend's computer in order for the state to be restored.
Another option, you can also pause the VM, then move the VM to your friend's computer.