Display featured image file size, extension, filename, type, orientation?

Question 1: use wp_get_attachment_metadata in the Codex
or the search function on this forum!

Question 2: Put this in one of your functions. It will echo the Alt text for the image.

$img_id = get_post_thumbnail_id( get_the_ID() ); //Note: you may need other methods to get id
$alt_text = get_post_meta( $img_id, '_wp_attachment_image_alt', true  );
if (!empty ($alt_text) ) {

    echo 'The Alt text: ' . $alt_text;

} else {

    echo "No cigar!";

}