So ideally, it would be better if you pick that phone up and dial the number to your nearest Reliance Digital and Digital Xpress Mini Store before walking into it. This way, you would know beforehand if you will be able to get the SIM with your 4G phone or not. The folks at the Reliance Digital and Digital Xpress Mini Store would be very discreet when talking to you on the phone. He/she will tell you that you can get the free SIM with any 4G phone, if the store has already been intimated by Jio. Additionally, he/she will also ask you to carry two recent passport-sized photographs along with a valid photo (and address) ID, for instance your Aadhaar Card (original and a photo-copy), to the store. You are also required to carry your 4G-compatible handset to the store. But, no other information will be provided. For instance, I was curious about the whole procedure involved here, since earlier you required a specific Preview code (a bar code) to get the SIM.
Speaking of which, you don't need to generate the Preview code anymore (Samsung and LG phone users still have to generate that code, by the way). The code will be manually provided to you at the store itself. You might want to download and install the My Jio app and the entire suit of 11 apps that come bundled inside, on your phone though.
It's legit: Reliance Jio Preview scheme now open for all 4G-enabled smartphones : News, News - India Today