MrClifford, thanks for the answer!
I'm talking about the second option.
Because in first case (if a user goes to purchase the IAP and decides not to go through with the purchase) - event "On product ... purcases success" won't happen, as I understand. So it's not a problem.
About second case - it's weird that we can't control it.
Because Google stores data about what the user owns.
So if user doesn't have product - i want check it and turn off the access to the content.
dop2000, yes, i tried using condition "Has product".
But the problem is that the validation doesn't work perfectly:
If you wait for the registration of products and check the condition "✖ Has product", then sometimes everything works as it should, and sometimes this conditions works even if the product purchased! :(