The Google Safe Browser API permits parts 1 and 2: https://developers.google.com/safe-browsing/
I'm not sure what can be used to filter adult content. Google images have filtering: you can check if the image from the site is blocked using a secure search.
Edit: To find out if a domain has adult content, enter it in the Google Image Search: site: domain.com safe = active
you can do this with safe deactivation, and if the difference in results exceeds a certain threshold (i.e. 10%), you can say that the site has adult content.
Edit 2: You may be able to check the meta tag and description tags (not all sites have them). They may have some dead prizes (keywords like βpornβ or βsexβ, etc.).
Tyzoid
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