Hi Amy!
It sounds like you’re getting ready for a fantastic day of park-hopping fun! With your Park Hopper ticket, you can absolutely start your morning at
EPCOT, scan in, and if you’re able to snag an Individual
Lightning Lane pass, you should in theory be able to ride
Guardians of the Galaxy: Cosmic Rewind, even if you’ve reserved your Lightning Lane Multi Pass selections for
Disney's Hollywood Studios later in the day.
It is my understanding that with a Park Hopper, you’re allowed to purchase up to two Individual Lightning Lane experiences for those high-demand attractions not included in the Multi Pass. I did call today and spoke with a Cast Member, who said that the system should recognize your Park Hopper ticket, allowing you to book Single Pass selection at a different Theme Park. Please remember, policies can change at any time so be sure to check back often.
Just keep in mind that return times are always subject to availability, so it's a good idea to plan ahead and keep track of your attraction windows. Enjoy your adventure and have an incredible day at both parks!
~Heather