You can use all features and plugins indefinitely. The only restriction is that you cannot re-open saved projects until you purchase a license.
Files labeled as "cracks" or "keygens" often contain Trojans, ransomware, or spyware designed to steal passwords and personal data. You can use all features and plugins indefinitely
If you want to try FL Studio without the security risks of a crack, the official developer provides legal options: specific build for compatibility
If you need an older, specific build for compatibility, Image-Line maintains a secure archive for registered users. You can use all features and plugins indefinitely