every media already expected that iOS8 will not introduce anything revolutionary and they were right.

iOS8 basically gives the iPhone what it should have but with a different interface, that's all.

to me, overall iOS8 should give better user experience.

so a soft reset (ie. Power + Home) and then when the phone restarts, run the native weather app. you'll be back to normal but make sure location service for weather is turned on.

syncing with iTunes doesn't require network connectivity.

i've tried once before with my 5S. i didn't not turn off the "Cellular Data" but turned on the "Flight Mode" because some say it will charge up faster however i have not tried restoring a backup before though but i think network connectivity should be also be irrelevant here as the backup data doesn't gets uploaded to iCloud servers or any other Apple online servers. there are actually stored in your PC.