In order to retrieve YouTube or Facebook comment links, simply right click on the time of comment, then select “Copy Link Address”, then paste it in a new tab and check if it will take you to the comment you are looking for and if it does then you’ve done it correctly!
Find the timestamp that is located next to your username above your comment (for example: "3 days ago") and hover over it then right click and "Copy Link Address". The link will be something like this: https://www.youtube.com/watch?v=12345&lc=a1b21etc instead of just https://www.youtube.com/watch?v=12345 To be sure that you got the correct link, paste it in your browser's address bar and you will see that the comment is now the first one below the video and it says "Highlighted comment".
Impression means reach (also how many users have seen your post) it is mostly used with brands, they will ask you to show them statistic of the impressions your posts have.
Instagram Saves is when a user saves a post to his history on Instagram (by pressing the save button near the like button). A lot of saves for a post increase its impression.