1/ You may change the design with your custom CSS which you may add just for AMP version -> https://xstore.helpscoutdocs.com/article/118-custom-css-section
2/ Only the existing ones are possible for this time. You may leave the request on our roadmap and once your request will be popular we will make it ready. But please, search before posting for similar questions maybe there are already created ones and you may only add your voice for it. https://www.8theme.com/roadmap/
One standard license is valid only for 1 project. Running multiple projects on a single license is a copyright violation.