1. because of caches
2. the result is identical./ Updating through Kies is called sideloading (download to your PC–transfer/upload to your phone–Apply update). OTA omits the fist stage.
3. related to your phone’s radio (depending on local regulations and frequency). Usually no difference for most countries.
4. Only when you try to flash your phone with unoffcial ROMs.
5. No.
