Hello,
Did you change code in wp-content/themes/xstore? If not then you won’t lose changes after theme files update.
Can you login and confirm the code has been saved in headers and footers plugin correctly so that next time I update the theme I don’t lose the YouTube subscribe button?
Take my apologies but we are not personal developers to help with the third-party customization https://themeforest.net/page/item_support_policy Mentioned buttons is not built-in option, so you need to check the documentation by yourself if you added everything according to requirements. Or hire developer here.
If you added code in Insert headers and Footers plugin settings you won’t lose it after theme update.
Regards