For 1, you’ll need to use an options page and add it as a sub page of any other pages you have for the plugin.
As far as 2 goes, this is possible. You’ll need to define your field groups in PHP and add them based on the selections. I generally built the groups in ACF and then export them. Once I have them there I start break them apart and building the code to add them where and when they need to be added
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