don't repeat posts from tags

Hi!

I have found this interesting code that shows thumbnails of posts that have the same tags, and not only the first tag, but also the following tags.
Which is great!

[Code moderated as per the Forum Rules. Please use the pastebin]

But I want to improve it 3 ways.

1st.- unfortunately it shows as well the thumbnail of the current post, in each tag…so if there are 3 tags, it appears 3 times. Can we remove the repeated thumbnails?

2nd.- if the found post has 2 or more coincident tags with the current post, I would like to show it’s thumbnail only in one tag list, not in every tag list, in order to not repeat it as well.

3rd.- Before each list of thumbnails belonging to a tag, I want to show the tag description.

Thank you very much for your answer!!!