a. The subject's clothing is red, which suggests he may be wealthy. This also means he is a cardinal, as stated in the title of the portrait.
b. In the background, there appears to be countryside, which may suggest calm. The colors are mostly cool colors. This likely also suggests that the subject is a calm person living in a calm environment. This is an important part of the painting.
c. The artist wants the viewer to see the subject as cool, calm, and collected. The subject appears to be half-smiling, which may suggest sprezzatura, which is being cool in Renaissance Italy. Also, the color scheme and background suggest calm.
d. This person's name is Edmund, and he is a wealthy and highly regarded cardinal. Edmund is a pretty cool guy. He likes his religion, as he is a cardinal, an important religious figure, and he cares about his job, because he gets to serve his god.