The link in the deal goes to an unofficial recording (albeit good) - but it doesn't zoom in to all the animation details projected on the castle. If you search for "Happily Ever After fireworks" and choose the video from the "Disney Park" channel, that is the official one, that has better audio and also zoomed in to see the animations at various times. However, its not in 4K as the video linked in the deal button.
Not with American Attractions who I bought them from, if I wanted 2021 tickets, I would have needed to return them and pay £300 extra. Anyway, not risking booking for next year and any travel insurance will exclude covid related claims.
If your tickets were the UK Ultimate ones Disney have auto extended the usage date till Sept 2021 (same price)
Sorry can just imagine how frustrating hoping you can get there soon 🤞