I have just started with cs50 and registered via EdX as auditing the course, now I noticed the lectures linked on EdX are noted as 2019 on Youtube while a new session is going on as 2020 on Youtube. What's the difference between the two? Will it be okay if I do the old ones to get the certificate or maybe do as many new ones as I can before I run out of them and then stick to the old ones to finish the remaining ones?
I haven't yet seen the 2020 ones, so I am not sure if there are any changes in the curriculum. But since the EdX course right now is built on the curriculum from the course of 2019 (PSETs, etc.) I think it would be best to simply follow the videos of 2019. It's perfectly fine to stick to these videos and finish the certificate - CS50 is taught every year, so there will be a new one every year
Most likely there will be an updated version of the EdX course next year.