Taking backup of IMEI:

MTKDroid Tool

  This is also very important,because many times installing custom ROM IMEI lost occur.

Connect your phone to PC USB debugging enabled.

Open Mtkdroid tool.Click on ROOT if root shell not enabled.After enabling root click on IMEI/NVRAM.

Then click on Backup.

                                                                        

                                             

                                          

                                       

You will get tow files inside Backup NVRAM folder Inside MtkDroid Tools folder.One is .bin and other in .tar format.save them for future use.

         

                         Now whenever you need to restore your IMEI,open Mtkdroid tool in the same way explained above and in place of backup click on restore.separate window will open two times,select .bin and .tar files respectively and your IMEI will be restored.