Two figures can be recognized as congruent if they have the same shape and the same measures. Both figures can be translated, reflected, or rotated and they will continue to be congruent.
Two figures can be recognized as similar if they have the same shape and all of its measures are proportional, i.e. all the measures of one figure are half the measures of the other figure.
The first pair of figures are squares, but their measures are not equal, thus they are not congruent. But we can see the smaller square's measures are all half of the other square's measures, thus they are similar.
The second and the last pair of figures are congruent. They are just rotations of the very same shape and measures, thus:
The second and the fourth pair of figures are congruent and not similar
Finally, the third pair of figures are made of a circle and an ellipse. They don't have the same shape. This disqualifies them to be congruent or similar
The third pair of figures are not congruent and they are not similar.