Theme extension and custom application development.

Hello.
I am new in shopify app development. Currently, I am creating one Shopify app. In this app, I give some customization to the admin. I created one setting page and in this page, I created a form with some previews.

  1. My first question is, is there a standard available for creating forms on this page? Currently, I am using Bootstrap and Polaris for creating form components.

  2. How to get store details for fetching customized data from our database in the remix page? Currently, I am using authenticate. admin(request) like this but continuously I get un authenticated error when I go to another page and then try to customize details.

  3. Currently I am using Bootstrap & Polaris for design when I save details in the database that that time my design changes and form preview does not show properly. how do fix this issue?