Whether you're a veteran speedrunner or a newcomer to the series, this version of Sonic Generations
Even with a pre-patched repack, users report issues. Here are the fixes:
To fix this, you need the game to be on the latest patch (v1.0.0.10). Since you cannot use the Steam updater on a repack, you must manually patch it.
Early PC releases used Denuvo Anti-Tamper. The "patched" repack includes a cracked Steam emulator (often based on SSE or Goldberg emulator) that removes online checks, allowing offline play without Steam.