Title says menu, just make sure to allow the permission to "appear on top" so the menu can pop up. Ias far as checksum hash, imagine you have a toy box with many different toys. If you want to make sure no one has taken any toys out or put any new ones in, you might count all the toys. A file checksum hash works in a similar way but with files on a computer. It creates a special number (called a "hash") based on all the tiny pieces of the file. If even one tiny piece of the file changes, the hash will be different, just like if one toy is missing or a new toy is added, your count will be different. This way, you can easily check if the file is exactly the same as before.
