2) You didn't give me that information. To find which map is installed, look in the device menu under Version Info
3) As you can see, it gives you the bootloader version and navcore (application) version. If you don't know what they mean, try google
4) 7.903 is still the latest navcore for your particular model
5) v885 maps are the latest. Which map (country) are you after?
6) To install a navcore, simply copy paste all the files and folders of the navcore onto your TomTom drive, overwriting any common files when prompted.
To install the latest map, the Tutorials section has it all. Exact 7 simple steps are right here:
7 simple steps to update your device with the latest map
To read the compatibility chart you mentioned, look at the vertical column 7.9XX - that is your navcore version. All the ticks indicate that those maps are supported for your device.