Hello, Not sure if all these questions have yet been answered, so I will try.
1) I have an A550 that also has been bugging me for months with the Reset Date & Time window when I power the unit on. Out of frustration one day, I pushed the menu button and the Reset Date & Time window closed. I was then able to use the camera without further issue. Keep in mind, you will need to repeat this process each time you turn the unit on.
2) In my camera, the CR1220 battery is located under the main battery access cover and inside a tiny lift out tab with the # CR1220 stamped on it.
Trust this helps.