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Miniature soft robots have shown unprecedented safe access in the hard-to-reach complex regions of nature, given their small dimensions and compliance by design. These machines are thus promising for novel biomedical applications, environmental stewardship, and beyond. While various miniature soft robots have been demonstrated, high-performance miniature soft robotic systems for task-oriented locomotions and functions have not been properly achieved. Particularly, the development of systems for task-oriented locomotions and functions is insufficient. Moreover, the improvement of these systems for fast and energy-efficient locomotions and multiple functions is unavailable. These challenges restrain the potential real-world translations of this unique robotic group. To this end, task-oriented locomotions and functions were addressed by properly developing the miniature soft robotic systems, including robot bodies and relevant systems. First, we addressed the challenge of designing bistable anchoring devices in tubular structures and the corresponding reliable medical imaging-based control system. While the stable anchoring state enables the robot to withstand the peristaltic forces in tubular structures for local functions, the stable relaxation state allows the manipulation of robot locomotion. Moreover, effective robot tracking utilizing medical imaging is necessary to deploy medical devices safely. In this study, the magnetic soft millirobot and actuation system were chosen, given their wireless controllability and the realization of the bistable states. Moreover, ultrasound imaging, known for its non-ionization principle, portability, and real-time imaging capability, was integrated into the control system for the robot's robust tracking and closed-loop manipulation. The effectiveness of the system has been validated experimentally. The proposed tracking method could also be extrapolated to other miniature soft robots for potential medical functions. While focusing on tubular structures, we further explored the design of millirobotic structures and their accompanying spatial actuation system for the regions with dynamic flow. Such a new intervention paradigm is critical given the various devastating diseases around distal neural arteries and the difficult conventional catheter-based access. The wireless soft millirobot was designed to be stent-shaped for its adaptability, low fluidic drag feature, and maneuverability in the lumen with the flow. Supported by controlled interactions with the solid boundaries, various locomotion capabilities were enabled and evaluated, such as the retrievable shape-adaptive locomotion for varying lumen diameters, self-anchoring to withstand the flow, curved route, and branch traversing. On top of the design, two potential medical functions were incorporated, i.e., flow diversion and on-demand local drug delivery by the remote heating of the SMP-based foldable structures. This new distal intervention paradigm has been compared with the conventional approach in the phantoms emulating the distal arterial regions and showed advantages in accessibility, interaction forces, delivered drug dosage, and adjustability. Based on the knowledge of developing task-oriented miniature soft systems, we then investigated how to further improve the performances for fast and energy-efficient locomotions and multiple functions. Fast and energy-efficient undulatory propulsion, one of the most widely spread locomotion modes, is critical for long-term operations. Although numerous studies have focused on the inertial flow regime, the intermediate flow regime was not well studied due to the lack of effective robotic tools. Therefore, we designed a class of untethered undulatory milliswimmers and magnetic actuation systems with the advantage of wireless operation without the negative effect of driving cables on hydrodynamics. By experimentally optimizing the body stiffness distributions k and actuation signals, we have emulated critical features of morphology, body kinematics, and wake flow patterns as larval zebrafish at both dimension and time scales using the novel robotic platform. The effect of k was systematically studied, and results revealed that combining high frequency and uniform k is energy-beneficial. On top of the knowledge, the shape memory polymer (SMP)-integrated wireless swimmer capable of adjusting k on the fly was further evaluated and confirmed the conclusions. Besides its impact on the autonomous underwater robot, this study could inspire wireless medical devices for targeted cargo delivery. While maintaining the high-performance propulsion, we explored the mechanism for multi-functionalities, which could be beneficial for various real-world tasks, in the final part of this thesis. Inspired by jellyfish's energy-efficient locomotion and contactless object manipulation, we developed a jellyfish-like robotic platform via an optimized synergy of electrohydraulic actuators and a hybrid structure comprising both rigid and soft components. As a result, the robot could propel fast, efficiently, and silently, which could accomplish possible safe interactions with the underwater species. Moreover, multiple functions were realized, such as contact-based and contactless object manipulation, fluidic mixing, shape adaptation, and steering. On top of a single robot, multiple agents could be individually controlled and form a team to enhance object manipulation. Finally, a wireless prototype, with all control electronics and batteries onboard, was developed and tested outdoors, indicating the potential feasibility of such compact miniature robotic systems for future field operations.