Every version of a sidecar has a minimum, maximum and recommended Kubernetes version that it is compatible with.
Minimum version specifies the lowest Kubernetes version where the sidecar will function with the most basic functionality, and no additional features added later. Generally, this aligns with the Kubernetes version where that CSI spec version was added.
Similarly, the max Kubernetes version generally aligns with when support for that CSI spec version was removed or if a particular Kubernetes API or feature was deprecated and removed.
It is important to note that any new features added to the sidecars may have dependencies on Kubernetes versions greater than the minimum Kubernetes version. The recommended Kubernetes version specifies the lowest Kubernetes version needed where all features of a sidecar will function correctly. Trying to use a new sidecar feature on a Kubernetes cluster below the recommended Kubernetes version may fail to function correctly. For that reason, it is encouraged to stay as close to the recommended Kubernetes version as possible.
For more details on which features are supported with which Kubernetes versions and their corresponding sidecars, please see each feature's individual page.
It is also important to note that alpha features are subject to break or be removed across Kubernetes and sidecar releases. There is no guarantee alpha features will continue to function if upgrading the Kubernetes cluster or upgrading a sidecar.