Samsung galaxy S4 Black Edition Downgrade from Lollipop to Kitkat

Hi Guys,

My Phone Samsung Galaxy S4 Black edition(India INS) got automatically upgraded to 5.0.1 Lollipop from Kitkat 4.4.2.
Since the upgrade i feel there a performance issues in my phone.
Now,I have decided to Downgrade it to Kitkat.I have identified the correct firmware from SAM Mobile below,

Model GT-I9500
Model name GALAXY S4
Country India (Black Edition)
Version Android 4.4.2
Changelist 923538
Build date Wed, 05 Mar 2014 07:25:51 +0000
Product code INS
PDA I9500XXUFNC1
CSC I9500YDDFNC2

I know all the procedures to Flash the firmware using Odin.

I have few questions below,
1)If i downgrade to the above kitkat version,Will i face Null IMEI problem and why?
2)I have also heard,the workaround for the null imei issue is to flash the modem.bin from lollipop firmware,then Baseband version will be still from Lollipop.Will this create signal problems in future?

Please share yours views and suggestions on this.

Thanks