I was able to activate JIO unlimited preview offer on Le Eco Le 2 mobile. Below is my experience in activating same.
Generated code on Le 2 using method suggested with old .apk file.
Got JIO sim from Reliance Digital ( Bangalore) after submitting required documents.
Received application submission request SMS in 2 hours and then tele-verification message within 2 hours and connection was ready in next 30 mins for making/receiving calls as well as data.
I had some issue regarding activating JIO unlimited preview offer on Le 2 (tried all suggested methods as per Google but results was negative)
Called JIO Customer Care and raised a Service request with them on 27/Aug for JIO unlimited preview offer activation. Agent had collected information on Device Model, Serial No., IMEI1/IMEI2.
Called them again on 28/Aug (Sunday Afternoon) and received update that I need to finish 2GB default data and 6 hours after that JIO unlimited preview offer will be activated automatically, without any action from my side.
Again called then on 28/Aug (evening - within 6 hours of finishing 2GB data) and received information from agent that the JIO unlimited preview offer is available only on specified phones and not on all phones.
After talking to third Customer Service Agent lost hope of activating and left phone untouched.
Today morning (29/Aug) received SMS on phone updating that your JIO unlimited preview offer has been activated and when verified inside My JIO app can see the message with unlimited access till 26 Nov 2016.
Now Data & Calls are working without any issue.
Seems JIO is not restricting activation of JIO unlimited preview offer on specific handsets.
JIO unlimited preview offer can be activated from Back-end also in case of issue in activation through MYJIO app.