I tried to get attachment meta caption value as mentioned here, but couldn`t get any output. Other meta arrays like [created_timestamp] or [iso] gave their values.
$img_meta = wp_get_attachment_metadata( $id );
echo $img_meta[image_meta];
This issue happens to both and [title]. Any help is much appreciated.
The caption and title you are looking to get from wp_get_attachment_metadata are not the title and caption you add in WordPress they are meta data from the actual image itself. To get the WordPress data use something like this (assuming $id is the id of your image).
Since WordPress 4.6.0 there is
get_the_post_thumbnail_caption($post)
which gets you the caption for the specified post.put this in your functions.php file:
and below the image in your theme, or wherever you prefer to put it, usually in the single.php file: