In most biological and artificial systems micro-swimmers are found swimming in confinements, e.g., sperm cells in the female reproductive tract, targeted drug delivery and biofilm formation. Though the motility of micro-swimmers is well-studied in unconfined fluids and near flat surfaces, the effect of confinement on the motility of micro swimmers is not well understood. Experiments show that confinement alters the dynamics of individual swimmers as well as their collective motion. Therefore in this work we first investigate the hydrodynamics of single micro swimmer in confinement and then the interaction between a micro swimmer and a passive particle in confinement. In the former case we find that strong pullers and pushers slide along the channel walls, a behavior determined by single wall. In contrast, swimmers with weak force dipoles break the symmetry in behavior between pushers and pullers. Weak pullers stay at the channel center and weak pushers execute an oscillatory trajectory spanning the channel width, the behaviours determined by both walls of the channel. Coming to the second case, a microswimmer interacting with a passive particle in confinement is driven by simultaneous, three way hydrodynamic interactions between the microswimmer, the passive particle and the microchannel walls. Therefore, in this work we investigate the hydrodynamic collision between a model microswimmer and a passive particle using three different methods: (i) the point particle approach, (ii) analytical calculations based on method of reflections, and (iii) lattice Boltzmann numerical simulations. We show that the hydrodynamic collision is essentially an asymmetric process - the trajectory of the microswimmer is altered only in an intermediate stage while the passive particle undergoes a three stage displacement with a net displacement towards or away from the microchannel walls. The path of the passive particle is a simple consequence of the velocity field generated by the swimmer: an open triangle in bulk fluid and a loop - like trajectory in confinement. We demonstrate the generality of our findings and conclude that (i) the microswimmer path is not significantly altered due to hydrodynamic collision with a passive particle in confinement and (ii) the net displacement of the passive particle due to collision may be capitalised in order to develop applications such as size separation of colloidal particles and deposition of particles in the microchannel interiors.