Here's the plan:
!!!!ONLY FOR THOSE WHO HAVE SUCCESSFULLY UPGRADED TO GEN2 WITH THIS GUIDE and have correct IMEI but after downgrade to GEN1 with THIS GUIDE have a fake IMEI (000039.....) even with the channel1.nvm trick method.!!!!
-On your phone upgraded to GEN2, install stock-recovery (credits to hecatae) Flash this with cwm. Warning, you won't be able to boot on cwm but you have stock recovery, FTM mode....
-Then reboot your phone and hold "Volume -" in the same time. Your phone show FTM now.
-download the two files here. (thanks to you burstlam)
-Follow instructions on this page but DO NOT DO ALL THINGS AFTER POINT 5 !!!!!!
-Simply tick "RF/BT/IMEI/unlock info" and "nv backup" option
-If you have the program configured as say in the instructions you can press "START ALL" button
-It will backup your NV data, it will take 1 minute or little more.
-When "PASS" appears in Green in the top-right corner, it's finish.
Now, you must downgrade your phone to GEN1. You should know how to do that now. I will not tell how to do cause there's two or more solutions I think, with maybe differents partitions layouts... You must have a wrong IMEI, wich begin with 000039.... with your GEN1 phone anyway.
Now you are on GEN1, flash again the stock recovery we have download before.
Boot on FTM mode with ''Volume -''. Run again the burstlam program just like before (as ADMINISTRATOR), and this time simply tick "RF/BT/IMEI/ulock info" and "nv restore" option.(RESTORE not BACKUP )
Press "START ALL" button again and this time it will restore your NV data. When "PASS" appears again in top right corner, exit the program, reboot your phone and tada ! Your IMEI is back. After that simply install cwm again or what you want. And do not play anymore with GEN2 upgrade Windows flasher.
Hope this help, if I say bullsh*t please tell to me. I'm not responsable if you kill your phone, it's simply what I have do and this work for me.
Thanks again to burstlam and leromarinvit.
EDIT: oops sorry Mahendra Soni, post in same time.
You have to replace splash or something like that. I use the files folder of THIS for the GEN2>GEN1 downgrade and it contain the green man android. Search in theme tutorial you will be able to replace the splash screen easily I think.
Edited by CaptainSpectacular, 23 April 2011 - 10:49 AM.