Q90T smart tv developer mode

  1. TV shows developer mode but still unable to delete default apps ie emanual, Netflix etc
  2. Which IP address to use DNS or not. IPV6 or IPV4?
  3. When I try to set up “develop” account, I get invalid email?

It does not sound like you are a Smart TV developer partner, so this question will be removed soon.
But some answers, There are things that can’t be altered such as an eManual that is built into the system or preinstalled apps.

Smart TV Developers partners have to be approved by Samsung. You can develop for your personal or business use in Developer Mode.

Samsung Developer Program