Applied compression to the game's assets, but the launcher won't run

I tried compressing the assets using tools like PNGoo and Fre:ac to reduce storage needed on my phone. The folder structure and filenames remains the same, so I tested launching my shrinked files with the PC launcher before transfering it to my phone, but the game won't launch, saying that some files are unreachable. Is the game coded to only recognize files if they are of the exact size and/or bitrate of the release?

Correct, you can override this with env[verify]=none in ons.cfg.