(x,y) -> (-y, x) This is a symmetry with respect to y=x, followed by a reflection across the y axis. Congruent.
(x,y) -> (x-2, y-1/2) This is a translation, but it follows different rules for each coordinate. Not congruent.
(x,y) -> (2x, 2y) This is a dilation. The resulting triangle will be similar, but not congruent. Not congruent.
(x,y) -> (-x, y) This is a reflection across the y axis. Congruent.
(x,y) -> (1/2x, 1/2y) This is a dilation. The resulting triangle will be similar, but not congruent. Not congruent.
