Yes, you can make this ahead of time. I would actually cut the dough first and then freeze so they are ready to bake. Here is my favorite way to freeze cookie dough: https://cookiesfordays.com/how-to-freeze-cookie-dough/

Yes! The shortening in the frosting will help it crust over so they can be packaged.

You can buy it in stores or on Amazon.

Hi! Great question. I actually developed a line of extracts and flavorings. You can find my cake batter flavoring here: https://shopcookingwithkarli.com/products/cake-batter-flavor-cooking-with-karli-1-oz-bottle

No, this icing will not work as royal icing. But if you’d like to put royal icing on these cookies, that would work!

Yes, that should work!