Yes, you can now do INR transactions in these 18 countries. I am not sure whether UPI transactions can be made but you can use your Indian debit card to make payments in INR in these countries. I do not think CBDC will be used for global purposes in the beginning. It is too early to discuss about it now.
I checked what @pakhitheboss wrote and found that it is all about Dedollarisation. It has nothing to do for someone traveling to these countries and trying to make purchase with INR. Making purchase with INR will happen if trade continues to happen in INR and not USD in these countries.
Another country has now become a part of this list. Please add Bangladesh on that list.