Issue with OAuth flow when reinstalling app from Uninstalled tab

[Arifursdev]

I'm trying to build a custom Shopify app that handles installation by the shop domain.

flow works like this:

• the merchant enters shop domain (abcd.myshopify.com)) in form in my app example.com/install
• then redirected to Shopify for approval,
• then back to my app URL where I exchange the $_GET['code'] for an access token and complete installation.
• After that, redirects to the app preview page on shopify iframe app view. https://admin.shopify.com/store/abcd/apps/abcd-plugin-app

The problem happens when the app is uninstalled and then reinstalled from Apps > Uninstalled. In this case, Shopify does not redirect to my app URL again, It just goes to the app iframe view, and no $_GET['code']parameter is provided, so I cannot regenerate an access token.

It gives these params in iframe view
'embedded', 'hmac', 'host', 'id_token', 'locale', 'session', 'shop', 'timestamp'

Questions:

How should access tokens be regenerated when an app is reinstalled from the Uninstalled tab?

Alternatively, is there a way to prevent the app from being reinstallable from the Uninstalled list and require installation only via the app URL? (like the Shopify GraphiQL App)