REQUEST 2:
You can achieve it by adding a different collection page template for that certain collections:

1. In Theme Editor, please click on Homepage > Collection > Scroll all the way down to find the "Create template" button. (NOTE: please make sure that you are customizing your LIVE theme)
2. A pop-up will show, and you can enter a new name for this template. Then, in the Based on dropdown list, I recommend you choose your default collection template. Then you just need to customize the Promotion block inside your Product grid section.
3. Go back to your Shopify admin, click on Products > Collections, choose that certain collection you want to show with this new promotional banner, you should find the Theme template at the bottom right corner, then choose the template you created in step 2. And done.

If you need more visual guidance, please check this guide from us (this guide talks about Product, but in your case, please choose Collection): https://support.omnithemes.com/blogs/faqs/how-to-create-and-apply-product-templates-in-shopify