Shape-shifting solvent-responsive hydrogels have emerged as a critical material platform for the development of soft robots, sensors, and actuators. Generally, to achieve actuation under different environments, using a layered structure with heterogeneous properties is a prevalent approach. However, the non-uniform force distribution at the interface between the layers can induce material delamination, thus greatly compromising the system’s stability and applicability. In this work, we present the fabrication, design, and analysis of a reversible and structurally stable single-component Functionally Graded (FG) hydrogel thin film. The fabricated film can actuate in both immersed and non-immersed aqueous environments. Thus, eliminating the requirement for a layered structure while retaining all its functionalities. A coupled diffusion-deformation framework using the Finite Element method is employed to comprehend the mechanism and understand the factors governing the actuation of the thin hydrogel films under different environments. The simulation curvatures and concentration profiles from different scenarios elucidate the influence of crosslinking gradation, water diffusion, and thickness on the folding behavior of the films. As a prospective application, we demonstrate the design of different underwater grippers using geometrically engineered symmetric and asymmetric graded films. To find the physical origins of deformation at the macro-scale, a thorough understanding of the structure-property relation between polymer and solvent is essential. Therefore, experiments are performed on thin hydrogel films under different environmental conditions using Nanoindentation and Dielectric Relaxation Spectroscopy. It is noted that the interplay between solvent-polymer interaction and subsequent polymer chain relaxation in the micro-scale leads to the observed macro-scale structural response. Thus, the present study attempts to gain a deeper understanding of the behavior of solvent-responsive hydrogel systems through experiments and simulations. Given the number of factors involved in designing a stimuli-responsive system, the above findings provide valuable insights into various aspects of hydrogel behavior spanning a wide range of environmental conditions.