I found this as an outdated topic in this forum.
Jamie, Chief Officer of Funness wrote that there is a code you can use to achieve an order minimum display at the checkout site.
It is the following code to be used in the cart. liquid where you can replace the existing button with it.
Now, it worked on my site, but the issue I am having is that the cart won't update automatically.
Briefly described, let's say someone adds items to get over the amount needed, the checkout button won't show up automatically, only when the customer refreshes the site. This of course also means that, if the customer now reduces the items in the cart and gets under the requested amount, the checkout button will still show.
So basically there is an info that there is a certain order amount needed where usually the checkout button would be placed, but it will not be updated automatically according to the amount in the cart.
I think to solve this would be great, not only for me but many Shopify customers who I am sure to have the same issue!
I already thank everyone who wants to help and I am looking forward to reading your replies.
To prevent checkout if minimum order value hasn't been reached on the static cart.liquid, you follow the advice given in the thread you linked above.
To prevent the CART button being active or shown in the slide out, you need to edit your theme.js - probably around cartPopupTemplate and some of the AJAX cart stuff.
Hope this helps!
Have you tried contacting Shopify design team support? If you used a free Shopify theme they can possibly help yu if the change falls within the scope of free support.
If not, you still have the option to either contact a Shopify Expert or any capable web design freelancer who should be able to implement such a feature.