Make two address fields in opportunity , correspondence address and permanent address. We have to fill both the fields with different addresses, if anyone of them is empty then generate message, and if the checkbox is selected then both the addresses should be same.

pls code it asap

I have a lightning app which has the remote site settings dynamic.
So, is it a good practice to use metadataService.class (http://technome2.blogspot.com/2017/05/creating-remote-site-settings.html) in post-installation script to add remote site settings for the org?