If shopify version upgrade breaks design of the existing website? Does Shopify support provide free of cost Shopify store fixation service?
Hello there Joy @joy_d Shopify updates are not to affect the look and feel of your theme in any considerable manner. You can find more information on this here https://help.shopify.com/en/manual/online-store/themes/managing-themes/updating-themes
If you do notice that you usually have store design issues after updates, then maybe you should reach out to Shopify customer support.
If you upgrade your theme from previous version to latest then by default there is no issue cause of break the design. It cause issue when you add a custom coding in your theme. Because the when a theme is update it remove the custom coding that you used in your theme.
The other thing you ask is there any free way who update your theme free of cost. The answer is No. Because it is time taken Process and need to take a look each of the theme. But if there is short custom code then I can help with that.
Thanks