Timeline answers:
In “We are Both,” Regina tries to run away before the wedding. It’s said that the wedding is in 2 days’ time when Cora vines her, according to Cora. She goes to her father the next day, as they say the wedding is “tomorrow.” She summons Rumple that night. The day of the wedding, she pushes Cora through the looking glass into Wonderland. Presumably she begins her training later that day when she’s riding away, and tries to give Rumple back his magic book. That’s when he asks her how it felt to do magic.
So ALL the training with Rumple is after Cora goes to Wonderland. No way around it.
That does make the letter confusing…but Rumple DOES occasionally like to gloat, especially with people who have badly hurt him.
Keeper of Belle's Gold magic, sand dollar, cloaks, purple FTL outfit, spell scroll, library key, copy of Romeo and Juliet, and cry-muffling pillow, Rumple's doll, overcoat, and strength, and The Timeline. My spreadsheet: https://drive.google.com/file/d/0B6r8CySCCWd9R0RUNm4xR3RhMEU/view?usp=sharing