1. You must have a BLACKBERRY data plan on your account in order to have a browser. No Blackberry Data Plan, no browser, no email, no internet...sorry.

2. 4.2 OS is not available for the 7105t, and probably never will be. The latest OS for the 7105 is 4.1. You can get more info on which versions of 4.1 are available here:

Latest Operating System Available For Each Blackberry Device