During the 2020 Covid lockdown Niall McLeod, RYA Racing Services Manager, produced a really excellent (in your Sailing Sec's opinion) series of six video lectures introducing the RRS. He subsequently added a 7th video covering the changes contained in RRS 2021-2024. I think these are so worth watching I've added a page on our website with a permanent link to them. Check them put - they're well worth watching.
You might also want to have a look at Allen Brothers RRS Rules Chart - a great overview and interesting way to test if you really know as much as you think you do!