Virtual reality rehabilitation (VR) can complement traditional rehabilitation therapy to increase motivation and thus the quality of exercise, while transferring effectively to real-world tasks. Hand tracking can significantly improve usability and immersion. A VR hand-tracking-based interaction system has been developed that supports various hand interactions, including grasping, pinching, and gesturing to complete virtual exercises. Interactions support modifiable difficulty and requirements, metrics, and visual error augmentation (EA). Audio-visual signifiers and feedback to guide interactions are also applied. A proof-of-concept rehabilitation game was tested with non-expert (N=7) and expert occupational therapy (N=5) participants. Participants completed tasks including grabbing objects, pinching, pulling handles, tracing paths, and making hand gestures. The system's usability was the primary outcome of the study. The results have shown this system is highly usable, with a modified System Usability Scale (SUS) of 88.93 (non-expert) and 74.5 (expert). A preliminary performance analysis was also conducted, indicating a limited number of unsuccessful hand-object interactions, although the accuracy in some interactions was impacted by tracking occlusion.