[en] The Standard Model (SM) of particle physics is a well-tested and predictive theory, being celebrated as one of the most successful models in newer time. However, non-zero neutrino masses, the existence of dark matter, and the baryon asymmetry suggest physics beyond the SM since the SM is not capable of explaining these phenomena. Thus, in order to have a model consistent with observations, a more complete theory is needed. There are several Beyond the Standard Model (BSM) scenarios which can replace the SM, and each of them lead to different new physics signatures. Experimentally, one can search for new physics, either producing it directly in particle physics experiments or indirectly by observing deviations from the SM prediction. This makes it possible to test each BSM scenario, and we consider both possibilities in this thesis. We consider BSM scenarios in the quark and lepton sectors, and study their phenomenological consequence on measurable observables. A specific example studied in this thesis is sterile neutrinos, and we consider sterile neutrino masses at the eV, GeV and 10¹² GeV scale in the context of symmetry-generated or structureless neutrino mass models. For the GeV sterile neutrinos, we find a distinct hierarchy among the flavor-dependent active-sterile mixings in the symmetry-generated mass models, which acts as a model discriminator. Considering 10¹² GeV scaled sterile neutrinos, they can, when combined with thermal leptogenesis, generate the baryon asymmetry in addition to small neutrino masses. As a result, either a broad or peaked sterile neutrino mass distribution is predicted from symmetry-generated or anarchical neutrino mass models, respectively. Anarchical neutrino mass models with eV sterile neutrino leads to either flavor-independent or flavor-dependent active-sterile mixing distributions, depending on the method used in the analysis. Similarly as using symmetries in the neutrino sector, one can also use symmetries in quark mass models. This thesis consider symmetries capable of quantizing the Cabibbo quark mixing angle to leading order. As a result, a variety of possible symmetries are obtained, which can be used to build specific quark mass models. Probing BSM physics indirectly via astrophysical neutrinos, acts as an alternative to direct detection, and using the neutrino flavor composition as observable, BSM physics leads to clear deviations from expectation. Additional information comes from other effects, and it helps in constraining the parameter space further. Beside discussing different BSM scenarios, we illustrate the potential of future experiments, emphasizing their effectiveness to test and discriminate BSM physics.