Dynamic caching and NGINX setting

Hi, Thanks for this great plugin. I have some questions.
1. I am using this plugin with NGINX. Without Nginx header shows ETAG, but with Nginx it doesnot show ETAG but show page expire time. Is pages are caching with NGINX or not?

2.My post contains dynamic a url of other host and i don’t want to cache that url. May i know is this plugin not caching that url but the whole post?

Thanks.