1) You don't. It is pre-installed with the OS and doesn't have a seperate version number.
2) Settings > General > About > Version
As for the other question in the subject, you cannot cancel the purchase now, 2.5 months later. Follow the instructions at the link below to downgrade your storage from the start of the next billing year:
and read: http://support.apple.com/kb/PH12796
Your post heading and the following questions are not related.
I believe that the safari version is tied to the ios version your using
go to settings/general/about/version
as far as your icloud storage, there isn't really way to cancel, it ends a year from date of purchase.
You can try contacting apple support and see if they will cancel it for you