Sonic Boom was once known as “Sonic Synergy”
The website for Edward Moore, a UX/UI design consultant on Sonic Boom, reveals that the Wii U and 3DS games were known as “Sonic Synergy” at one point.
Moore’s site also houses images of UI diagrams and early concept artwork. Another image – shown below – also seems to depict a slightly different-looking Sonic.
As The Sonic Stadium points out, “Sonic’s arms are back to being tan in colour, spikes are also different, much more like the Sega Sonic version. Amy also has some differences too.”