You can't use your Gmail address at the moment, because you changed it to the new iCloud address. It would be the same as before: no apps, no icons in Safari. It would be a completely new Apple ID. You'd have to change it back again on the website (Manage Apple ID).
Did you open Safari (the app) and take a look at it?
Btw: you don't have to erase all content and settings to change the Apple ID. That can be done in Settings - iTunes & App Store, without losing apps.