The biggest changes are at the Webelos & Arrow of Light levels. I took screenshots from the youTube video Cub Chat Live February 2nd 2024 so everybody can see the slides at a glance. AFAIK the slides are not posted anywhere else to link.
There will me more details coming as the program rolls out, but this gives a primer.
Yes, AoLs can wear the green scout hat if they want to.
https://www.scouting.org/program-updates/cub-scout-program-updates-faq-1-3-24/
Individual requirements probably won’t change a whole lot, so it’s possible to take some guesses to get adventures on the calendar and then confirm once the books are available.