Do I need to sign out of one All app to use it on another All App?

The license is for one All App at a time. You can remove the license on one to be used on another.

Access the teacher mode. If you are in Student mode, select Teacher mode in the top left corner.

Select Help and tutorials

Select About

Select License Info

Before deactivating take a screen shot or write down your license key!

Select deactivate

To activate the All App 
Access the teacher mode. If you are in Student mode, select Teacher mode in the top left corner.

Select Help and tutorials

Select About

Select Activate to the right of license number

Enter the license code and activate