Yes they both have to work simultaneously but we can remove ipv4 once ipv6 started working
Not 100% true. either the Home Gateway should support Dual Stack or ISP should implement NAT64 in case using V4 content. As far as i know SLT is ready but the cost of CPE are preventing but they should not have an issue with LTE.
Dialog එකට call කරලා කිව්වම පැය 2කින් වගේ ipv6 active කරා. උබලත් කියලා කරගන්න.