Which resource provides documentation and downloads for Sitecore products prior to version 8.0?

The Sitecore Developer Network is the correct answer because it serves as an extensive resource specifically tailored for developers working with various versions of Sitecore products. It includes documentation, downloads, and community forums that focus on technical aspects and guidelines for Sitecore, especially prior to version 8.0. This platform is valuable for accessing legacy information and tools necessary for development with earlier Sitecore releases.

The other options, while they each provide useful content related to Sitecore, do not specifically focus on or provide access to documentation and downloads for versions prior to 8.0. The Sitecore Developer Portal is geared more towards resources for current and newer versions, while the Knowledge Base is a support resource that primarily offers solutions for existing problems rather than comprehensive access to older documentation. The YouTube channel is designed for video content and tutorials rather than serving as a repository for technical documentation and downloads.