In the recent years ferromagnetic shape-memory alloys (FSMAs) with a coupled magneto-structural first order phase transition have attracted a lot of interest due to the presence of latent heat of the structural transformation. In these alloys metastable states are formed due to the competition between thermal and magnetic energies. The strong coupling between the magnetism and structure in these kinds of materials results an entropy change when magnetic field is applied. The first order martensitic transition (MT) has been observed through magnetization and electronic- and magneto-transport measurements in Ni45Mn44Sn11 disordered Heusler alloy. The sharp change of magnetization from ferromagnetic austenite phase (AP) to weak magnetic martensitic phase (MP) in the vicinity of MT leads to both large magnetic entropy change and negative magnetoresistance (MR). The alloy also shows a second order ferromagnetic (FM) to paramagnetic (PM) phase transition above MT. The maximum magnetic entropy change at 275 K for the application of 5 T magnetic field are 24 Jkg-1K-1 and 15 Jkg-1K-1, estimated from field decreasing M-H protocol and field increasing M-H protocol, respectively. The maximum MR of -16 % and -43% for the field change of 8 T is observed at 275 K, when the temperature is reached by cooling from 320 K and by warming from 150 K, respectively. The difference in AP and MP phase fractions, originated from different thermal path and magnetic field path, is the most possible reason to observe different values of entropy change and MR in Ni45Mn44Sn11 Huesler alloy. First order MT in Ni45Mn44Sn11 also shows field induced effect. The field induced MT has been confirmed from the magnetic measurements and electronic transport measurements under high magnetic field. Arrest of AP in the MP by the application of magnetic field has been observed from both magnetization and electronic transport behaviors. It is also clearly seen that tuning of metastability due to the coexistence of AP and MP can be done by external parameters like magnetic field and temperature.