Question 1: You are correct.
Question 2: Download, then extract with 7zip. Put phone into download mode. Open Odin on computer and connect the phone. Place extracted md5 into the pda slot and hit start. It'll do it's thing and your phone will reboot and be done.
Question 3: Yes as long as don't take the OTA update from Samsung you will able load roms as usual
Can anyone give me the download link for MJ9 OTA Firmware by Beans?
Thanks