Reactive oxygen species (ROS) play important roles in pathophysiological processes. A large number of pathological conditions are associated with over production of ROS. Therefore, there is widespread interest in developing ROS-responsive linkers for targeted drug-delivery and imaging applications. However, in such studies, there are major concerns of inappropriate use of various methods that lead to erroneous results. Along this line, we have described several factors that reshape ROS research. First, we critically analyzed the literature in combination with our own experimental findings, dissect complex scenarios into bite-sized problems, and provides practical and straightforward tutorial steps to follow in assessing the feasibility of a particular method for a given problem. We specifically proposed analysis of the interplays of ROS Stability, reaction Kinetics, Additives (e.g., solvent, buffer, and cell culture components), ROS and probe Concentrations, and probe Selectivity to set up the SKACS guardrails against some common pitfalls for ensuring experimental rigor and data quality in ROS research. Second, we described how DMSO and commonly used organic buffer components consume highly reactive oxygen species (hROS, anything more reactive than H2O2) before the probe at commonly used concentrations. Such rapid hROS consumption by DMSO and organic buffer components can lead to false negatives and misidentification of ROS. Third, we described how cell culture media creates hROS signal in the absence of cells by activating added H2O2. These results change the assumptions of this widely used method to create a cell culture model for redox mechanistic studies. Collectively these findings impact the entire ROS-related research. Fourth, with all these understanding, we developed a novel HOCl/OCl--selective prodrug approach for targeting desired cell type. Specifically, the prodrug approach is based on oxidation-initiated Cascade Reaction with Kinetic Tunability (CReKT) for drug release. HOCl/OCl- are primarily produced in response to infection and/or inflammation by certain immune cells that express myeloperoxidase (MPO), therefore providing targeting to pathological conditions. This approach offers new tools and sets a new direction in designing species-selective ROS-sensitive prodrugs. Overall, this dissertation provides fundamental insights, guidelines to follow for future ROS-related studies, and new tools for ROS-sensitive drug delivery and/or imaging agent.