Ni-Mn-Ga compounds have drawn considerable attention in this millenium after the discovery of considerable magnetic field induced strain required for actuator applications. The prototype Ni2MnGa in the family of Magnetic shape memory alloy (MSMA) family has been investigated in detail. Mn2NiGa is a recently discovered member in the family which has a simple (Inverse) Heusler crystal structure. However, due to a chemical composition and site ordering different from Ni2MnGa, this material gives rise to interesting structure-property relationships. In this talk, I would discuss how the site ordering impacts phase stability and electronic, elastic and magnetic properties in pristine and transition metal substituted Mn2NiGa. A comparison with Ni2MnGa based compounds will establish the fascinating possibilities of Mn2NiGa based systems exhibiting multiple functionalities like shape memory effect and high spin polarisation upon substitutions. The fundamental physics governing the properties will be discussed in detail.