I want to return back to the free trial since I started the store to learn and added my credit card to be able to do the whole buying process until checkout. So how can I return back without closing the store ? I don't want to get billed because this is a test store and I will do the official store next month when I am ready.
Ted here from Shopify, thanks for reaching out to us!
It wouldn't be possible to return to a free trial as your store is still currently on a free trial until you receive your first invoice. As this is a test account, I would recommend closing the store on the 13th day of your 14-day free trial just to ensure that you do not receive an invoice. If you decide that you would like to re-open the store again for testing purposes, I'd recommend contacting our support here or here for further assistance as we should be able to add another trial extension to the account, as long as an invoice has not been issued previously.
I'd like to note that if you would prefer to have a full-time account available simply for testing, then to consider creating a Shopify Partner account. A partner account is used by developers to help build Shopify sites for clients, create apps, themes, refer people to Shopify or to have a test account of their own. It's free to use/sign up for and more information can be found here. There's some great Partner content available here too which might peek your interest if you're interested in the development side of things. Alternatively, Shopify Compass offers a wide range of tutorials such as SEO and marketing courses that might suit you as well.
If you decide to open a Shopify Partner account to have access to your own development store; you can duplicate your current store's data as and then transfer it to a new account as outlined in this doc.
Let me know how this goes and if there is anything else I can help you with, I'm happy to help!