[Title should read "app.sis vs. app_installer.sis".]

Hi, I'm a bit confused about which SIS files to submit for publishing to the Nokia Store. I'm targeting my app to three platforms: S60 5th Ed., Symbian(^3) Anna, and Symbian Belle. I've built with Qt 4.7.3 as this is compatible with those three platforms (more or less--and the VKP 4.7.4 seems to have a cursor positioning bug). This has generated several questions:

0. Should both the app.sis and app_installer.sys (both unsigned) be submitted for each platform or just one for each?
1. There are separate Qt 4.7.3 build target libraries for S60 5th Ed., Anna, and Belle. Should I just build for the lowest platform and expect the app to run on the newer ones? Or should I build for each platform and submit three content files? (The app does not use newer features introduced with Anna.)
2. In my testing, I found that the S60 5th Ed. platform devices require the app_installer.sys but the Anna and Belle could install with app.sis (the later come with Qt installed). So, for S60 5th should I add a content file entry with app_installer.sys and and for Anna and Belle the app.sys file?