For your 1st question
First on your store layout, in the
1-On start of layout, use the Add product ID action to add the product IDs you will be using, e.g. "product1,product2,product3".For your 2nd question
2-After that (still in the 'Start of layout' event), use the Request store listing action. This starts downloading the names and prices of the given products. Some platforms require this information to be available for the IAP features to work.
3-When On store listing success triggers, the product names and prices are available, and purchases can start being made or checked with the Has product condition.
So after this point you can do a purchase, on purchase successful you can store a variable on web storage or wherever you want but make that variable is persistent.
Then have your extra content to check every time for that variable, if its set then show your extra content, if its not set then you should not show it.I still havent experimented with restoring, I will tell you when I get it