Thank you for your detailed response.
Just to explain what prompted me to start this discussion:
1. I have been reading many posts here that 'services', including data/MMS/Personal Hotspot etc. will be available if iPhone is used on a 'Supported carrier' and poster pointed to Apple Support Doc. http://support.apple.com/kb/ht1937
2. There is a fair percentage of iPhone users, which includes me, who want to use 'officially unlocked' iPhones on carrier(s) not listed in the Support Doc. in 1. above
3. There are some recent posts complaining about APN settings not being saved after updating iOS to 7.1. Even though Apple stated in their doc "The settings should save automatically"
Best