my MacBook has the screen currently off and VO doesn't recognize commands

Hi all mac users I am new on the Mac world, I am learning voiceOver commands and all kind of system with Mac OS. I have been using a MacBook around 2 weeks and I don't know how to set up and how to work on it, I press for accident some key and the Mac condition is the fallowing, the screen is currently off and voiceOver doesn't recognize the keyboard for some reason I modified all the keyboard. one example of this is whenever turn off or on voiceOver I need press command + f5, and previously was control + option + f5. first I guess need to reset voiceOver settings and later how to fix the issue about the screen off. . I do not know how did this just I knew this because one friend of mine asked me why do you have the screen off? Please help posting good comments. remember explain step by step how could I do it, I can not make commands for the issue with the keyboard. I can go at the system/Preferences but just i don't know what step fallow to reset VO settings later. there is a command to change the screen currently ON/OFF?. I am running a MacBook Pro on Mac OS X Mountain Lion.