[T-Mobile Samsung Galaxy Note II] LanceDiamond:
Short answer: IMEI & baseband same as before the flash - both are "Unknown".

Prior to my messing with the dialer menu, everything was fine. I'd used Odin or TWRP recovery to flash a variety of different ROMs the last of which was the 4.3 we're talking about here and it was working. I'd used it for several days. Everything but screen mirroring worked without any problem and I had service - I read up on the screen mirroring problem and it sounded like getting the device to show "Official" might help so I tried to reset my flash counter which I did not do before going to 4.3. Flash counter wouldn't reset so I decided to go back as far as I could on modem/ROM and see if I could reset flash counter then. (I know my Knox flag is not fixable - I was just trying to change the flash counter.)

Using TWRP, I installed UVALJ1 modem & associated ROM, leaving the 4.3 Knox locked bootloader in place to see if that'd work. It did, it booted and I had service. I was actually playing with the menus to see if the old dialer code free unlock menu settings still seemed to work because someone had posted about needing to unlock - looked like the menus were still there for doing an unlock. In messing with the menus I picked the option that messed everything up and since doing that, no matter what I flash, IMEI & baseband are unknown.

Unless KIES rebuilds the entire radio - which it very well might based on it needing the correct model and then wanting a valid serial # - I think I need an efs restore to get the phone communicating with anything now.

One thing I just now did - using the free NV Items Reader Writer from this thread: http://xdaforums.com/showthread.php?t=1804117

On my Note 2 configured as "DM+Modem+ADB" in Qualcomm USB settings (the only of several dialer menus I know of that still actually exists & seems to work), I can see the modem & port in device manager. But the app cannot communicate with the phone. If I change nothing, unplug the Note 2, plug in my Galaxy S4 in "DM+Modem+ADB" mode, I see modem & ports pop up in device manager and now the app can communicate with the phone.

I'm afraid, based on the text of that warning and searching for what "AP" and "CP" are, that the phone isn't going to be able to communicate with much of anything until it gets its efs fixed. This test where I just swap phones seems to be comfirming that this phone isn't responding like it should. Basically my modem & the rest of the phone are disconnected right now - at least that's my understanding. If the modem really is disconnected then obviously trying to do something to fix it via the modem is never going to work. The KIES may work - if I can ever get it sorted out. Haven't yet tried it in a VM might do that right now...

Edit:

Got KIES3 & drivers working in Windows XP SP3 VM. KIES connects to phone but if I pick Tools/Firmware Upgrade with the phone connected it just says "SGH-T889 does not support initializing" and my only choice is "OK". If I go Tools/Firmware without the phone plugged in, I can enter the model # and then it asks for serial #. If I plug the phone in at the point it goes all the way to where it says it's downloading firmware and then same result as on Windows 8 - an AdminDelegator process gets started, KIES gets sort of dimmed like it's waiting on something and nothing ever happens. If I never connect the phone KIES goes through the downloading process then gets an error with options to send a message or cancel - no information about what the message is, what the error is - just I can send it, it won't contain personal information or I can cancel.