Add image file upload field to WooCommerce single products

You could try the following, that will store uploaded image data as custom cart item data and save it as custom order item meta data: 

// Display additional product fields (+ jQuery code)

add_action( 'woocommerce_before_add_to_cart_button', 'display_additional_product_fields', 9 );
function display_additional_product_fields(){
    ?>
    <p class="form-row validate-required" id="image" >
        <label for="file_field"><?php echo __("Upload Image") . ': '; ?>
            <input type='file' name='image' accept='image/*'>
        </label>
    </p>
    <?php
}


// Add custom fields data as the cart item custom data
add_filter( 'woocommerce_add_cart_item_data', 'add_custom_fields_data_as_custom_cart_item_data', 10, 2 );
function add_custom_fields_data_as_custom_cart_item_data( $cart_item, $product_id ){
    if( isset($_FILES['image']) && ! empty($_FILES['image']) ) {
        $upload       = wp_upload_bits( $_FILES['image']['name'], null, file_get_contents( $_FILES['image']['tmp_name'] ) );
        $filetype     = wp_check_filetype( basename( $upload['file'] ), null );
        $upload_dir   = wp_upload_dir();
        $upl_base_url = is_ssl() ? str_replace('http://', 'https://', $upload_dir['baseurl']) : $upload_dir['baseurl'];
        $base_name    = basename( $upload['file'] );

        $cart_item['file_upload'] = array(
            'guid'      => $upl_base_url .'/'. _wp_relative_upload_path( $upload['file'] ), // Url
            'file_type' => $filetype['type'], // File type
            'file_name' => $base_name, // File name
            'title'     => ucfirst( preg_replace('/\.[^.]+$/', '', $base_name ) ), // Title
        );
        $cart_item['unique_key'] = md5( microtime().rand() ); // Avoid merging items
    }
    return $cart_item;
}

// Display custom cart item data in cart (optional)
add_filter( 'woocommerce_get_item_data', 'display_custom_item_data', 10, 2 );
function display_custom_item_data( $cart_item_data, $cart_item ) {
    if ( isset( $cart_item['file_upload']['title'] ) ){
        $cart_item_data[] = array(
            'name' => __( 'Image uploaded', 'woocommerce' ),
            'value' =>  str_pad($cart_item['file_upload']['title'], 16, 'X', STR_PAD_LEFT) . '…',
        );
    }
    return $cart_item_data;
}

// Save Image data as order item meta data
add_action( 'woocommerce_checkout_create_order_line_item', 'custom_field_update_order_item_meta', 20, 4 );
function custom_field_update_order_item_meta( $item, $cart_item_key, $values, $order ) {
    if ( isset( $values['file_upload'] ) ){
        $item->update_meta_data( '_img_file',  $values['file_upload'] );
    }
}

// Admin orders: Display a linked button + the link of the image file
add_action( 'woocommerce_after_order_itemmeta', 'backend_image_link_after_order_itemmeta', 10, 3 );
function backend_image_link_after_order_itemmeta( $item_id, $item, $product ) {
    // Only in backend for order line items (avoiding errors)
    if( is_admin() && $item->is_type('line_item') && $file_data = $item->get_meta( '_img_file' ) ){
        echo '<p><a href="'.$file_data['guid'].'" target="_blank" class="button">'.__("Open Image") . '</a></p>'; // Optional
        echo '<p><code>'.$file_data['guid'].'</code></p>'; // Optional
    }
}

// Admin new order email: Display a linked button + the link of the image file
add_action( 'woocommerce_email_after_order_table', 'wc_email_new_order_custom_meta_data', 10, 4);
function wc_email_new_order_custom_meta_data( $order, $sent_to_admin, $plain_text, $email ){
    // On "new order" email notifications
    if ( 'new_order' === $email->id ) {
        foreach ($order->get_items() as $item ) {
            if ( $file_data = $item->get_meta( '_img_file' ) ) {
                echo '<p>
                    <a href="'.$file_data['guid'].'" target="_blank" class="button">'.__("Download Image") . '</a><br>
                    <pre><code style="font-size:12px; background-color:#eee; padding:5px;">'.$file_data['guid'].'</code></pre>
                </p><br>';
            }
        }
    }
}

Source: https://stackoverflow.com/questions/62847710/add-image-file-upload-field-to-woocommerce-single-products 

Remove jQuery Validate error class from input fields and apply on error labels only

 You can use the following method to remove error class apply on form elements.

$('#addNewForm').validate({

        highlight: function(element) {

            $(element).removeClass("error");

        }

});

Disable dynamic dropdown option value onchange another dynamic dropdown

I would make a function that checks every selected value, and then enables all options, searches through the .staff_lists for options in that array that are not currently selected, and disables them all.

Add that function as a listener to the wrapper (with event delegation) and run it after more <select>s are appended (to ensure the new options' values get properly disabled), and run it after <select>s are deleted (so that if that <select> had anything selected, its value is now enabled again in the other elements).

This ensures a correct re-calculation of disabled options whenever there's a change.

Note that because there are currently only 3 possible values (a, b, and c), only three selects can currently be changed - after that, every possible option (except the default) will be disabled.  

var add_button = $(".add_sign");
var wrapper = $(".sign");
var max_fields = 6;
var x = 1;


add_button.click(function(e) {
  if (x < max_fields) {
    x++;
    wrapper.append('<div  class="input-group sign_user"><select class="staff_list" name="staff_id"><option value="">--Select staff--</option><option value="a">A</option><option value="b">B</option><option value="c">C</option></select><span class="input-group-btn delete_sign"><a href="#" class="btn btn-sm btn-danger">X</a></span></div>');
    recalcDisabled();
  } else {
    alert('Maximum 5 Authorised Signatory only!');
  }
});
//Delete staff_list
$(wrapper).on("click", ".delete_sign", function(e) {
  e.preventDefault();
  $(this).parent('div').remove();
  recalcDisabled();
  x--;
});
wrapper.on('change', 'select', recalcDisabled);

function recalcDisabled() {
  const selectedValues = $('.staff_list')
    .map((_, sel) => sel.value)
    .get()
    .filter(Boolean); // Filter out the empty string
  $('.staff_list option').prop('disabled', false);
  selectedValues.forEach(value => {
    $(`.staff_list[value!="${value}"] option[value="${value}"]`)
      .prop('disabled', true);
  });
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="sign">
  <button class="add_sign">Add New Field &nbsp; 
    <span style="font-size:16px; font-weight:bold;">+ </span>   </button>
</div>
Credit: CertainPerformance (https://stackoverflow.com/users/9515207/certainperformance)
Source: https://stackoverflow.com/questions/51738465/disable-dynamic-dropdown-option-value-onchange-another-dynamic-dropdown