1) We are theme developers, we are not plugin developers, so we can’t recommend third-party plugins to our customers because of this. We are not fully familiar with all the options that third-party membership plugins have. We would recommend you read special articles, for example https://optinmonster.com/wordpress-membership-site-plugins/ and compare plugins, choose the one depending on your needs. Contact plugins authors and clarify all the questions related to plugin options. We are able to help you with theme settings only.
2) XStore theme does not have known compatibility issues with the membership plugins, so I don’t see reasons why you can’t use it for your site.
A) Ok, we are glad to hear that you already have some site. But could you clarify how it’s related to our theme? Did your developer build site using XStore and you have some issues?
B) Our theme is WordPress-based. So, we support all the default options for the blog that WordPress has. If you need more information about the WordPress blog page and WordPress posts system I would recommend you to watch youtube video tutorials for WordPress beginners.
C) We don’t have such system in our theme, so I suppose you need to look for Membership plugin that allows this.
D) What kind of emails do you want to send? Our theme supports default WordPress and WooCommerce emails. We don’t have any additional types of emails.
Theme supports MailChimp plugin, so you can have the newsletter form https://wordpress.org/plugins/mailchimp-for-wp/
Read the license policy https://themeforest.net/licenses/standard
You can use 1 license for 1 project(dev and production sites) according to ThemeForest license policy. So, if you want to create few projects you need a separate license for every single project.
