Using post thumbnails in a seperate template loop

I’m trying to add something into my theme and customize it.
This thing is called “tab” and I did not initially design it.
It basically functions as 3 custom loops and displays post titles.
What I’m trying to do is use it to display thumbnails in place of the titles.

To explain further the first loop pulls the most recent posts.
The second loop lists the posts by comment count.
and the third is a loop that displays random posts.

Here is the code:

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

The problem I’m having is changing the the titles into thumbnails instead.
I’m hoping someone who has a better grasp on scripting can help point me in the right direction or edit the code I posted and re-post.
Not sure why this I can’t get it to work so thought I’d ask here.
Even the last loop which looks fairly easy to change by replacing the “title” part with “thumbnail” isn’t as easy as I thought it would be.

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