Google Results Display by Request URL

I have a domain with many old non working subdomains.
Some subdomains have different pages- all not working if you try to access them.
Links to these subdomains and pages are on many websites but they all return 404.

For example there are links like this on different external websites:
subdomain1.mydomain.com/folder/page.html

subdomain34.mydomain.com/votes.php

What is needed:
If request URL returns 404, display a page with relevant Google search results.
Get the results from my API (or your API if the price is good).

How to display results:
Query API for the request URL
Take title (minus subdomain name if exists in title) and query API again for that title
Display 4-6 results on this page.
Store results in JSON in case this URL is requested again (to avoid API calls for this URL).

If Query API for the request URL returns no page title, query API for the subdomain of the request URL, return 4-6 results.

You will need to do it on your localhost, I cannot provide server access.

Any reply without " I have fully read and understood what needs to be done and I can do it on localhost " will be ignored.