The spin itself as in changing the 1/2 to 2/2? If so, no. It is not possible. However it is possible to change the direction of the spin, as in changing it from an up spin to a down spin.
Since E = mc^2, how can photons be massless? If a photon has no mass, then, according to Einstein's formula, its energy is given by E = 0 x c^2, which is 0. Yet, photons do have energy. This seems to be a complete contradiction. Please explain! Thank you.