We explore the possibility of formation of ∆ baryons (1232 MeV) in neutron star matter in an effective chiral model within the relativistic mean-field framework. With variation in delta-meson couplings, consistent with the constraints imposed on them, the resulting equation of state is obtained and the neutron star properties are calculated for static and spherical configuration. Within the framework of our model the critical densities of formation of ∆s and the properties of neutron stars are found to be very sensitive to the iso-vector coupling compared to the scalar or vector couplings. We revisit the ∆ puzzle and look for the possibility of phase transition from non-strange hadronic matter (including nucleons and ∆s) to deconfined quark matter, based on QCD theories. The resultant hybrid star configurations satisfy the observational constraints on mass from the most massive pulsars PSR J1614-2230 and PSR J0348+0432 in static condition obtained with the general hydrostatic equilibrium based on GTR. Our radius estimates are well within the limits imposed from observational analysis of QLMBXs. The obtained values of R 1.4 are in agreement with the recent bounds specified from the observation of gravitational wave (GW170817)from binary neutron star merger. The constraint on baryonic mass from study of binary system PSR J0737-3039 is also satisfied with our hybrid equation of state. 2:26 WSPC/INSTRUCTION FILE del˙q 2 Debashree Sen, and T.K. Jha and therefore they can be treated on equal footing along the nucleons. Moreover, owing to low excitation energy (m ∆ − m N = 293 MeV) and strong coupling with N-π system, ∆s often have various critical contributions to nuclear dynamics. 8 They are formed in neutron star matter (NSM) only as metastable resonance states and like hyperons, the appearance of the ∆ isobars depends strongly on the strength of coupling with mesons, which are largely unknown for the ∆s at present. In this work we study the possibility of formation of ∆ resonances in NSM and their effects on the structural properties of neutron stars (NS), with an effective chiral model for ∆ couplings that are consistent with available literature. However, it is well known that the formation of such exotic matter like hyperons or ∆ particles etc. in NSM softens the equation of state (EoS) considerably, reducing the maximum mass of the NS. This leads to the well-known hyperon and delta puzzles in light of the recent observational estimates of high mass pulsars like PSR J1614-2230 (M = (1.928 ± 0.017)M ) 9 and PSR J0348+0432 (M = (2.01 ± 0.04)M ). 10 Many works have suggested various ways to deal with these additional degrees of freedom and to solve these puzzles. Refs. 11-26 have dealt with the delta puzzle and refs. [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] with the hyperon puzzle, in a phenomenological approach (using both relativistic and non-relativistic treatments) while works like [45][46][47][48][49][50][51][52] have been done within the microscopical framework for the same purp...