Absolutely irrelevant to anyone's interests but it turns out that Sonic 4: Episode 1's android port, which has a tendency to barely work on modern devices (lacking sound) and for some reason runs like absolute crap on emulators like bluestacks, will work with sound effects on a retroid pocket flip if you start it up right after resuming from its sleep mode.
This has to happen after sleep -- simply starting the game after turning it on or a reboot won't work. I have no idea why it's like this -- the game hasn't seen an update in like 8 years, and I can't really blame them for abandoning it.
You probably wouldn't want to do this but I would suspect that it's the best way to play the game in its more-or-less 'native' habitat. While the default controller mapping of the game is incoherent (jump seems to be mapped to left-stick-click on every device and controller pairing I've tried; jump is enter and not space, and none of this is remappable), you can use the flip's button mapper to press the screen where the jump button is, and the d-pad works the way you would suspect it to.
More importantly, the original mobile version all support tilt controls for everything, and while I don't know that I'd recommend playing the game that way instead of touch controls, many of the game's bizarre design decisions (especially the use of the homing attack and the strange physics) make a lot more sense if you presume that the game was always designed with device-tilt controls in mind and screen-touch to jump. Sonic Runners is the better implementation of a similar idea (it's an autorunner reminiscent of canabalt).
The absolute strangest potentially-feasible way to play it, however, remains hacking a lenovo yoga to launch Brunch (chrome os) and running the game from there. Since the device has a tilt sensor (used at least for tablet-mode orientation) the game's tilt controls will work -- you're just playing on an impractically large device. Sound had no issue either, and my guess is that's because chromeos is doing some kind of high-level emulation to manage it. (Obviously, touch controls work and are a much more reasonable option.)