Continuing a "stopped" iCloud restore on iOS I was restoring my iPhone 5 to the latest iOS and chose restore via iCloud. The restore process - especially for apps - was frustratingly slow and actually stopped frozen after a while.

After trying several other options, I finally "Cancelled" the iCloud Restore operation and then manually installed the apps via iTunes, as well as synced songs, etc.

Now for some of the apps, data is missing and my Photos also appear to be incomplete. Since I "cancelled" the iCloud Restore (and was warned about not being able to do this again), is there any way at all I can coax iCloud into streaming the app data back into the installed app folders, as well as getting my photos? Would there perhaps be two separate ways of doing that?

Or is the only other option to "Erase Content and Settings" and do the restore process all over again, allowing Photos to restore gradually via iCloud, while installing apps via iTunes parallely (without "Cancelling" the iCloud restore)? 

If the answer to the last question is "Sadly, yes", then can it be assumed that if the app is installed via iTunes anyway, iOS will proceed to restore the app's data from iCloud? Or does the app HAVE to be installed OTA for the data to also be restored from iCloud?
iCloud could be slow in restoring especially if you have lots of app data and your WiFi is not Speedy Gonzalez. I have some bad experience restoring with iCloud as my Photos app and Spotify app are both more than 5 GB each. 

There is absolutely no way to let iCloud take over from where it left. You need to do the restore anew. 

I'd suggest, the next time backing up via iTunes or an alternative such as Copytrans Shelbee. The restore will go rather quicker as it is done over USB. The backup in iTunes is exactly the same as with iCloud (including app data).