Unlike the official Simply Piano app which receives regular patches, cracked versions do not get updates. This leaves your device permanently exposed to unpatched security flaws .
Using modified application files (IPAs) from unofficial sources like third-party "tweak" stores or forums can lead to: Malware & Spyware
If you have already downloaded a cracked IPA, it is highly recommended that you: Delete the app and any associated profiles in your iOS Settings. Run a security scan if you used a computer to sideload the file. Change your passwords
That being said, here's a general review of the Simply Piano app and some insights on the cracked IPA version:
Modified apps frequently suffer from lagging and freezing issues because they are not optimized for the latest iOS versions.