Theme development

Hello,
I am designing a theme that has a header image on some pages. The 'page' content type has an image field, which is pulled into views and thrown in a block at the top of the page. However, some pages don't have this image, and the design calls for a border line when the image does not exist.

So -- I'd like my main content region to know if this image exists and add appropriate style classes if not.

What do I need to do in my template_preprocess_region function? I can't find the appropriate variables for this case. I was thinking something like the following:

I am so new to this... I just need to change the top image of the website (link below) to another image. The website is using Drupal 6 and the blueprint theme. I am able to get to the theme building page, is that the right place to start?

http://www.ultravision.com.sg/

Thank you so much! I will really appreciate all the help that I get!!

Hi, I purchased a Drupal theme, not knowing it was made for Drupal 7 and not Drupal 8.

What is the easiest way to convert this theme over to Drupal 8? I've read this documentation: https://www.drupal.org/docs/8/theming/upgrading-7x-themes-to-8x

Please advise how I can modify the style of the navigation bar in the header, e.g. style of the logo image, such as width and height. I used Zen's StarterKit to create a sub-theme.

Please help me

My web alat pemadam api can not open and there is a message like below:

Warning: mkdir (): Disk quota exceeded in /home/u828661378/public_html/lib/classes/component.php on line 226

Unable to save the cache config to file.

Hi Guys,
I have one important question and need prompt and detailed answered please.
What makes a website search engine-friendly?
Thanks in advance.