Because 5.0a was a leak and the project was technically abandoned (with the team moving toward other projects), you will generally find it through community-hosted archives and longplays:
Searching for leads you to the pinnacle of ROM hacking. It is a chaotic, beautiful, and punishing love letter to the SEGA Genesis. It respects the original physics while mocking the limitations of the hardware. sonic megamix 5.0 online
Look for hidden "Big Rings" to enter Special Stages. You will need all Chaos Emeralds to unlock the true final boss. ⚠️ Common Fixes Game Running Slow? Close background browser tabs. Because 5