GIMP has no "Pro" version or paywall. A "crack" is trying to unlock something that isn't locked in the first place [1, 2].

These downloads often contain Trojan horses, ransomware, or spyware designed to steal your personal data or lock your files [3, 4].

Version 2.99.12 was a development "preview" release (part of the road to GIMP 3.0). Using outdated development builds from third-party sites can lead to software instability [5, 6]. How to Get GIMP Safely:

GNU Project - GIMP - Details on the open-source nature of the project.