Docs: Various

In some rare cases when visiting your site, it returns a blank page with the message XML-RPC server accepts POST requests only. First, make sure you installed latest available version of Swift Performance. If you need to update, rebuild cache after update and if the problem still persist, it coul...

Yes, you can enable it in Settings > Media > Images > Lazy Load. Then all of your images will be lazy loaded automatically.

You can exclude it through using: jscache.com/wejs in Exclude Scripts.

Try with deactivating "Force Responsive Images" feature: Settings > Media > Images >Force Responsive Images.

Please be sure that you are using the latest version of Swift Performance. If you do, enable Heartbeat in Swift Performance Settings if it is disabled. Normalize Static Resources in Settings > Optimization > General also can cause this issue, try to disable it if it is enabled.

Most likely your caching path had changed and you need to change that in Swift settings: Settings > Caching > General > Cache Path. If you are not sure about the new path you can reset section, Swift Performance will find the new path automatically.

Unfortunately not all iframe embedded videos compatible with lazy loading. You can exclude the problematic iframe, or disable lazy loading for iframes in: Settings > Media > Embeds

Every plugin can. If you have this issue, you should enable WP_DEBUG or check the PHP error.log to see what the exact issue is.

Yes, of course it does. Swift Performance also has some WooCommerce specific options to speed up your shop. You can find these options in Settings > Plugins > WooCommerce

Swift supports multisite by default, no special configuration is needed.