Thanks for your questions. Here are the answers to your questions.
1. Rick HTML build with HTML markup language and Rick React JS version build with React JS. They are different frontend technologies.
2. These templates are mainly used by developers who already know backend language ( PHP, Node JS ) or CMS ( WordPress ). They make these templates dynamic. So direct import like WordPress will not work with these templates.
3. On buyer request, we sometimes provide the landing page.
Hope these answers all your questions.