Thanks, this page has more info about it for those interested.
http://piiis.blogspot.in/2014/10/how-to-use-sprint-lg-tribute-with-page.html
I just did this and got my SPC by email immediately. You just need to input the MEID and the ICC ID, both are printed on the outer box itself. I had to add a payment method, but I used a Virtual CC added to an Amazon account and used that as the payment source. You do not need to perform the actual activation on the device, I don't think it would work from India anyway. I haven't got the device in my hands yet, just asked my friend in US to send a pic of the barcode at the bottom with the MEID info.
I suppose if you use a referral link, you would get 25 USD as Ting credit, so payment may not be required. If anyone is interested you may use mine -- https://z9q7jd3mm79.ting.com/