Welcome to two weeks ago

Upgrading to leaked RC of PR1.2 and then downgrading will disable the cellular modem (firmware of modem gets upgraded in the process, and it becomes inaccessible from PR 1.1.1). There are a few procedures to get back cellular capabilities on PR1.1.1...you can search for them in this forum. I have no idea how well they work, since I've not tried the upgrade, so YMMV....