No Return Policy
This is a great question and definitely understand the importance of getting information about this. Shopify doesn't manage the day to day business aspect of the stores on our platform, which means you can set up your own policies for customers to adhere to.
It is important to note that having a no refund policy does not stop customers from opening claims for various reasons with their banks. I strongly recommend reviewing our information on chargebacks or inquiries so that you can be best prepared for this: Chargebacks and inquiries · Shopify Help Center.
Having clear policies laid out for your customers is the best way to avoid any issues. I would definitely suggest having the information clearly laid out on as many surfaces as you can. I would look at adding the info onto the product pages, order confirmation emails, etc. Also, sending an email to the email address on file for a double confirmation and make a phone number mandatory at checkout as well. While it may seem to be a bit redundant, these steps can help you win a chargeback or inquiry and also weed out flaky customers.