First-principles calculations were carried out to investigate the electronic and magnetic properties of SnSe₂ armchair nanoribbons (ANRs) via edge hydrogenation. Interestingly, at different hydrogenation degrees, SnSe₂ ANRs exhibit versatile electronic and magnetic properties, i.e., from nonmagnetic-semiconductors to magnetic-semiconductors or nonmagnetic-metals. Through the analysis from spatial spin distribution and density of states, these transitions are well interpreted. Moreover, the relative stabilities of these ANRs were evaluated by the thermodynamic phase diagram where the Gibbs free energies as a function of the chemical potential of the H₂ molecule at different temperatures were plotted. Our results show that hydrogenation is a well-controlled way to modify the physical properties of SnSe₂ ANRs. Through controlling chemical potential or partial pressure of H₂, the different hydrogenation degrees of ANRs are thermodynamically stable, thus, one can arbitrarily steer their electronic and magnetic properties. The diverse electronic phases and magnetic properties endow the hydrogenated SnSe₂ ANRs with potential applications in nanoelectronic devices.