What's the control flow of global variables?

Control flow for blocks under event handlers run from top to button, but control flow for global variables confuses me.

What's the control flow of global variables?
Which global variables gets initialized first and are initialize global variable blocks run first before event handlers?

Global variables are initialized first, then the Screen.Initialize event is fired. The order in which global variables are initialized should be ignored. you cannot initialize a global variable using another global variable, so the order is not important. If you need to use some other global variable in another global variable, do so in the Screen.Initialize event.

If you initialize several local variables in one block, you also cannot use one variable to initialize another variable. You should then use the second variable initialization block.