The shock formation, their electromagnetic structure, and the injection of suprathermal particles into the first-order Fermi acceleration processes at collisionless shocks constitute important problems of high-energy astrophysics. We report on recent studies of high Mach-number nonrelativistic perpendicular shocks with fully kinetic two-dimensional particle-in-cell simulations in applications to forward shocks of young supernova remnants. We discuss a nonlinear shock structure mediated by electromagnetic Weibel-type filamentation instabilities and demonstrate the cyclic shock reformation and shock rippling processes known before only for low Mach-number shocks. We also analyse conditions leading to particle heating and pre-acceleration. We confirm electron injection through shock-surfing acceleration in the foot of high Mach-number shocks. We show that the injection efficiency is not stationary and varies with the phase of the shock reformation. It also nonlinearly depends on the upstream plasma temperature. Furthermore, we demonstrate that further electron energization processes in the shock ramp strongly depend on the configuration of the uniform perpendicular magnetic field with respect to the simulation plane, highlighting a need for a fully three-dimensional kinetic studies.