You are downloading the Sonic 4 Episode I XAP file v22.214.171.124 for Windows Phone. Sonic 4 Episode I is a free Action & Adventure Game: The sequel fans have waited 16 years for is finally here - SONIC THE HEDGEHOG™ 4 Episode I! Featuring enhanced gameplay elements, including the classic Sonic. You can now download the offline XAP package file to install & try it.
Download Locations for Sonic 4 Episode I 126.96.36.199 XAP file
To try to install it manually from an SD card, you should choose one of the server location above to get the offline Sonic 4 Episode I XAP file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.