Developer has replied saying that it being a web app is compatible with large number of Asha devices and that they have tested it on Asha 311 too. It is now available at Nokia store as a paid app, but the price is just 15 INR for India.
Current and future Asha 501 owners rejoice!! If you are using Asha 501 as your primary or back up smartphone and miss Instagram as your favorite application, then be happy!! Instagraph, first Instagram client with ability to upload to Instagram for Lumia devices is also coming to Asha devices. The developer of the application David Lorenzin from Venetasoft has been in touch and let us know about it. He has also uploaded a video at skydrive demoing Instagraph on Asha 501 and above is a screenshot from that video.
Thanks David for letting us know. Cheers!!