If an application has been previously tested with a Series 40 device and it is Java Verified, can I install the same application to other Series 40 devices?

There shouldn't be any problem with the installation itself. However, if the application has only been tested with one device, there's no guarantee that it will work in other devices. Therefore, retesting at least with target lead devices is recommended. Java Verified supported devices can be found at www.javaverified.com -> Table of supported devices.