Samsung Galaxy Note 3 — Note 3 SM-N900 Exynos IMEI null Baseband unknown

Note 3 SM-N900 Exynos IMEI null Baseband unknown
Android 5.0
Firmware N900XXUEBOE3_N900ODDEBOB2_N900DDUEBOB1 (India)
How did the problem start? – my kid was playing some game in the phone and when I got it back I noticed the problem. It wasn’t because of flashing custom ROM or rooting. It could be due to firmware upgrade as upgrading was set on automatic but not sure.
What all have I done to solve the problem?
1. Rooted the phone and checked EFS folder. The EFS folder did not have .nv_data.bak file. And I don’t have backup of pre-problem EFS folder.

2. Downloaded stock firmware, extracted the modem file (bin) and flashed it, both with odin and cwm. Didn’t help.

3. Downloaded and flashed with odin stock firmware Android 4.4.2 N900XXUENI1_N900ODDENF1_N900DDUENG1_HOME.tar.md5 AND also N900XXUENG1_N900ODDENF1_INU. Didn’t help.

4. With each of the above stock firmware I flashed the following modem files:-

(1) N900_XXUDNA1_MODEM_CWM
(2) N900_XXUENE1_MODEM_CWM
(3) N900_XXUENF2_MODEM_CWM
(4) N900_XXUENG1_MODEM
(5) N900_XXUBMI2_MODEM_CWM
Didn’t work.

5. Used EFS Tool Samsung N7100 900 to back up EFS folder of a working Note 3 SM-N900 and restored the backedup folder to my phone – didn’t work.

6. Tried GSII_Repair app (both with my own EFS folder and my friends EFS folder. – didn’t work.

7. Tried to install xposed to use imei changer app. But xposed did not install as it is not yet compatible with Android SDK version 21 or processor architecture armeabi-v7a.

8. Tried Kies firmware upgrade and initialization, SM-N900 does not support initialization.

9. Tried secret code and got to Service Mode. But service mode is like a blank page of a lined book – no options shown.

10. And I tried factory reset with each of the above firmwares. Did Factory reset and wipe cache partition before flashing new firmware – didn’t work. Then tried it after flashing – didn’t work.

11. Also tried *#197328640# or ##197328640## both didn’t work.

12. Tried fix by Firasusman Script / Fix Soft Brick Loop_ EFS partition_01.11.13

13. used advice of RuchRha flash bootloader zip and downgrade to android 4.3. now my phone is running Android 4.3 but imei null and baseband version unknown persists.

Can’t afford a new phone. Could somebody please help?