Adress Fields

To unhide the field labels, try this custom css:

.woocommerce form.checkout .col2-set p.form-row label {
  display: inline-block !important;
}

The code approach to changing labels and placeholders is described here:
https://docs.woocommerce.com/document/tutorial-customising-checkout-fields-using-actions-and-filters/

If you prefer a non-code solution, there are a few checkout field editor plugins that can do it.

Thanks!!!