"Good morning, are you Vera and Vanya?"
Translation:Доброе утро, вы Вера и Ваня?
You can use вы when you talk to "respected" person - teacher, or someone who is older than you. And ты you can use when you talking with your friend. BUT in this situation, you talk with 2 persones, so we ALWAYS use вы when you talk with 2 or more persones. I hope now it's clear
Short forms are only used as predicates. They are also in a quite intricate relationship with the full form, with stylistic complications we only glance over in this course.
This being said, using "добро" is not possible here anyway because it would not be idiomatic even were we to assume it grammatically correct.
Foreign languages/keyboards: The following is my experience using an Android Samsung S7 (I can't guess the navigation on Your device, but it's probably similar). Go to: General Management > Language and Input > Language > Add Language > follow the prompts to add as many languages as you want. After you've added a language, when you scroll your keyboard "space" bar (right/left) the keyboard changes to - in this case - Russian. I also emphatically suggest you download the SwiftKey keyboard app; it dovetails with Duolingo beautifully.