Absolutely! Magic Members’ installation is just like any other WordPress plugin. Just upload it and activate it.
Yes, you can upgrade your license in 30 days without paying anything extra. Let’s say you bought Single License for $97 and you want to upgrade it to Unlimited License which is $207. You pay only $110 to upgrade your license to Unlimited License. If you would like to upgrade your license after 30 days it will cost you an extra $47, so will need to pay $157.