1. Still not quite sure if I understand. Are you <div class="custom-optin-container">
?
How is that added?
2. How are you creating that? I would recommend our new plugin Generate Blocks:
https://generateblocks.com/
The grid column might be what you are looking for.
3. I’m not seeing the CSS that should make it center?
4. It disappears as it has hide-on-mobile
class added.
Not quite sure if these are GP related questions…more like custom development questions.
If you are not comfortable with HTML and CSS, then I’d highly recommend Generate Blocks.