Simple Wordpress prototype site supporting search and browsing of a closed index with two key features specified in project description

The attached json contains a nested tree structure of headings, sub-headings and topics. The purpose of the prototype is to enable a visitor to search or browse the index and then to select a topic. On selecting the topic, the visitor will be prompted to enter name, email, phone, company, city, province and country fields. The user will then be prompted to enter payment details. On completion, the selected topic will no longer be available for selection by an subsequent visitor. It should still be searchable, browsable and visible, but the text should be crossed out, and the selection box replaced with a message saying "no longer available". We intend to use Hubspot for the mail integration and Stripe for the payment, and we will add those integrations ourselves. What we need from the prototype is to mimic that intended behaviour but without any actual connection to a mail services or payment gateway. For purposes of assessing the prototype, we want you to host it. The project will be considered complete when we received the code and all explanations, and successfully mount it our selves on our own hosting platform. A milestone payment of 50% will be paid when we approve the work demonstrated as usable on your hosting site. The index should be presented to visitors in a way that lets them see the relationship between heading, sub-heading and topic. For example: <Heading> <Heading> -- <sub-heading> <Heading> -- <sub-heading> -- <topic>