In an organ pipe open at both ends, the air particles at the open ends are free to vibrate with maximum amplitude, forming displacement antinodes. A displacement antinode always corresponds to a pressure node. At a pressure node, the pressure remains constant (equal to the atmospheric pressure), meaning the pressure variation or pressure change is minimum (zero). Therefore, the statement 'Pressure change will be maximum at both ends' is incorrect. Additionally, for an open pipe, the allowed frequencies are integral multiples of the fundamental frequency ($f_n = n \frac{v}{2L}$, where $n = 1, 2, 3, \dots$), meaning all harmonics (both odd and even) are generated.