stretching a photograph
vertically or horizontally

Visually stretching a photograph either horizontally or vertically — even by a tiny bit — always disqualifies a photograph from P2.

That is because everything in the photograph is reshaped by such actions, and the only reason that anything in TTG photographs can ever be reshaped is to correct for lens/camera anomalies.

Note that cropping and overall downsizing do not disqualify photographs from TTG, as per the Allowables list.