I want to change the screen to multiple screen mode by pressing a random button
What exactly is a multiple screen mode?
Please elaborate
Taifun
I want a user to press a button to go to screen 2, but I don't want it to go to screen 2. I want it to be a random multi-screen one, like screen 3. It goes to screen 8.
put your screen names into a list, then use the pick a random item method to pick a random screen and open that screen
https://ai2.appinventor.mit.edu/reference/blocks/lists.html#pickrandomitem
Taifun
Sorry, I'm new. I don't know how to use blocks. I want you to explain to me how to install a block. Also a question: How do I put a screenshot? Here you can see it.
A very good way to learn App Inventor is to read the free Inventor's Manual here in the AI2 free online eBook App Inventor 2 Book: Create Your Own Android Apps ... the links are at the bottom of the Web page. The book 'teaches' users how to program with AI2 blocks.
There is a free programming course here Course In A Box and the aia files for the projects in the book are here: App Inventor 2 Book: Create Your Own Android Apps
How to do a lot of basic things with App Inventor are described here: How do you...? .
Also do the tutorials Our Tutorials! to learn the basics of App Inventor, then try something and follow the Top 5 Tips: How to learn App Inventor
Taifun
Trying to push the limits! Snippets, Tutorials and Extensions from Pura Vida Apps by 
Taifun.