I want to set up a digital nature trail with a video of information at each post. The QR code on the post will reference the video. The QR code (URL) must be permanent but the video will change with the seasons. Can I do this using YouTube for the video and URL? If not can you suggest an alternative access solution? We are a small voluntary organisation so free is best!
On Youtube each video has its own URL so it's not possible to use the same URL for different videos but you could embed a video on a web page and change the embedded video, so the web page URL will not change, only its content.
For general instructions on how to embed a video on a web page, see Embed videos & playlists. If you want to ask for a software recommendation consider to post a question on https://softwarerecs.stackexchange.com