We have witnessed a wide range of theoretical as well as experimental investigations to envisage external stimuli induced changes in electronic, optical and magnetic properties in the metal organiccomplexes, while hybrid perovskites have recently joined this exciting league of explorations. Theflexible organic linkers in such complexes are ideal for triggering not only spin transitions but also aplethora of various different responses under the influence of various external stimuli like pressure,temperature and light. A diverse range of applications particularly in thefield of optoelectronics,spintronics and energy scavenging have been manifested. The hysteresis associated with the lightinduced transitions and spin-crossover governed by pressure and temperature, are promisingphenomena for the design principles behind memory devices and optical switches. The pressureinduced optical properties tuning or piezochromism has also emerged as one of the prominent areas inthefield of hybrid perovskite materials family. It is thus imperative to have a clear understanding ofhow the tuning in electronic, optical and magnetic properties occur under various stimuli, andselectivity of the stimulus could be influential behind the maximum efficiency in thefield of energyand optoelectronic research, and in what future directions thisfield could be driven from theperspective of futuristic material properties. This review though primarily focuses on the theoreticalaspects of understanding the different mechanisms of the phenomena, does provide a unique overviewof the experimental literature too, accompanied by the theoretical understanding such that relevantdevice applications can be considered through a future roadmap of tuning paradigm of externalstimuli. It also provides an insight as to how energy and memory storage may be combined by using the principles of spin transition in metal organic complexes