We obtain several new sharp C-continuity conditions, both necessary and sufficient, for operators of harmonic reflection of functions over boundaries of simple Carathéodory domains in RN. These results are based on a new criterion (also obtained in this paper) for C-continuity of the Poisson operator in the aforesaid domains. As corollaries, we give new sufficient conditions for C-approximability of functions by harmonic polynomials on boundaries of simple Carathéodory domains in RN. Bibliography: 17 titles.