Sending variables between screens

blocks(2)

block1 is screen 2 and block2 is screen 3
here button image not changing
if condition not executing in screen2 only else

Why do you need multiple screens for this. Use virtual screens then all you problems go away

Use different screens wisely

If you decided to use different screens, then you should switch them correctly, else you will run out of memory after a while...      
The recommended method of switching screens in App Inventor
(Thanks Taifun)
 
Also see demo: multiscreen.aia
 

Hello there,
Yep, I pretty suggest you to follow TIM's hint. You can have as many as simulated screens avoiding problem of shared variables, by using the arrangements.
Take a look and try the annexed aia. I simulate three screens with fade-in and fade-out effects.
Hoping it helps.
Kind regards.
provafade.aia (1.4 MB)