In the previous episode Elizabeth gives Maggie keys so that she can get "the Boy" out of the royal wardrobe. It is snowy and there is snow on the ground. The next morning, no snow anywhere and sunny. Then later it goes back to cold and snow on the ground.
Teddy and "The boy" are shown being executed on the same day. In real life Perkin Warbeck was executed on Novemeber 23, 1499 and Teddy was executed 5 days later on November 28.
The curse was about firstborn sons. Lizzie and Henry didn't want to kill Prince Richard because of the curse but he was second son.