How long do I need to press & hold the buttons?

How long do I need to press & hold the Volume up key, power button and menu buttons.

When I press the Volume up key and the menu buttons at the same time, It says on the upper left on the screen *Recovery Booting* is it a good sign?

How long it will take to finished the recovery? Also, do I have to leave it plug?

Also, do I need to remove the Sim card & SD card?