Images in posts and homepage

Hi, I have a few questions about images:
1. How do I get an image in the post header? I have set one in the featured image box, but it’s disappeared from the blog header.
2. Once I have an image in the post header, how do I change the colour of the floating heading over that image? I had an image with a white background before it disappeared, and the text overlayed white so you couldn’t read it. I only want to change it on one page.
3. I can’t work out how to put a full-page image at the top of my home page. I’ve chosen the ‘Home: Classic’ homepage. It looks like there are two images, one in the background and maybe a png with a transparent background in the foreground. Firstly, where would I upload those images, and secondly, if I only wanted one solid image, where would I upload that.
4. Without having sample images load with the demo I’m not sure how to size some images. What size should this homepage splash image be optimised to please?
5. On an internal page, I used just the text field, then a single image field as the only two blocks on the page. The image is not sitting full screen. How do I fix this? I already have ‘Full WIdth Section’ selected.

Thanks in advance 🙂

Ticket