Calendar post thumbnail image

Here’s one that I feel has a simple solution but I have not idea how…

So, I’m building a template and using <?php get_calendar(); ?> I’ve put a calender in a custom single post page for the category ‘blog’. There are 2 things that I want to do with this and I can’t find a solution of either despite there being a few posts about this topic. So forgive me if I sound like a broken record player:

1. Display posts in the calender from a certain category ID (‘blog’). I think this is to do with the general template functions template.

2. Using advanced custom fields to call <?php the_field(slideshow_image); ?> (which is just an uploaded image inside the post’s admin page) add a thumbnail to the permalink of that blog post. So the everyday on the calender that has a post on it has a picture on it.

I know some of these topics have been touched on before but please don’t take this as laziness – I’m really struggling for a robust solution. And I shouldn’t be putting 2 questions in 1 but I feel they are very similar and can therefore be killed by 1 php stone. Please cast your stones my way.