DX(G) Update DX (B00801) to 3.x firmware

[matopeto]

Hi all

I recently bought Kindle DX model B00801, which seems has only 3g and no wifi

I want to upgrade to 3.x firmware because of better browser (and run my https://github.com/matopeto/kindle-weather-dashboard on it)

I read about that i must have kindle 3 to make image of system, and than update my DX

Here are my question:

1. can be used firmware from kindle 3 wifi (no 3g) (maybe i somewhere have one)
1a) if i don't find kindle 3 there is other possibility to get correct firmware?
2. i i flash with correct firmware, would be 3g connectivity works? Or device will be without any connectivity?
3. Can I after upgrade safely revert firmware back to 2.x (do i need backup or can i download original firmware)

Thank you for all answers