Hi. This is what Instagram says about the error you are receiving.
We're aware of an issue where some people get a "Device not compatible" error message in the Google Play Store when trying to download Instagram, even though Instagram should support the phone. Google is currently investigating this issue with Google Play Store.
As a temporary workaround, Google suggests clearing Google Play Store's data from your phone and then trying to install Instagram. To do this, go to Settings > Application Manager > All > Google Play Store > Clear data.