Hi,
So on your Shopify cart theme you want:
1- when the user is hovering her mouse over the cart icon, in the main page, it says the massage as an Alert.
2- In the check out page, if the final price is less than 200 it pops up the same message while the free shipping option is not available (not selectable) and the other option is selected by default.
This would take three days max.
Thanks,
Hoofar