Grub 2 - settings
 

I have a multi-loading system with Linux and Windows 7, but I don't want to see menu on the screen, but have possibility to choose one of the system during boot. Can I do so?
Also I'd like to rename Windows 7 to another name, for instance - "Old testing system" etc.

Take a look at post #2 at the ubuntu forums site below. It explains the GRUB_HIDDEN_TIMEOUT feature. If you don't see the menu, you will need to remember which entry is which so you can arrow down to the one you want. Can't see the point in this but it's your computer.

http://ubuntuforums.org/showthread.php?t=1280943

If you want to rename windows 7 in the Grub menu, just change its menuentry line in double quotes. I'm not sure why you would want to do this if you don't want to be see the menu?

I think about ways to make my task either hide or rename it. Where can I change its menuentry line? In /boot/grub/grub.cfg file? But it'll change after upgrade Grub again.

Change the name to whatever you want on the windows menuentry line as in the example below, the part in double quotes. If you do not run update-grub and reboot you should see the entry. It should not change if you do not run update-grub or do a system update. If you want it to be permanent, copy the new windows entry to the /etc/grub.d/40_custom file and save it, then run update-grub.