Magento – How to get the product id and SKU code of the product selected

Looking at your code, you are missing the part where you inform Magento which attributes are used in your configurable (this would correspond to the first step when creating a configurable product in the admin, where you pick the used attributes). Put this before the call to setConfigurableProductsData:

$mpr->getTypeInstance()->setUsedProductAttributeIds(array(85,192));

If you add a custom options to a product you can add, for example for dropdown options, a product sku suffix as shown below.

On choosing an option when adding the product to cart and retrieving the SKU in the cart var_dump($_item->getSku()); you can see the products SKU has been changed

Now for dynamically updating the SKU on the product page. For this we will need to retrieve the option values SKU's which can be done in the file app/design/frontend/[package]/[template]/template/catalog/product/view/options.phtml for example. In this case around line 190 after the javascript we add/replace some code as shown below. This will give you a javascript array which you can use when a custom option is selected to map the option ID to the SKU suffix and changing the displayed product SKU on the product page.

<dl>
    <?php $options_to_sku = array();?>

    <?php foreach($_options as $_option): ?>
        <?php echo $this->getOptionHtml($_option) ?>
<?php
if ($_option->getType() == 'drop_down')
{
    $options_to_sku["{$_option->getId()}"] = array();
    foreach ($_option->getValues() as $k => $v) 
    {
        $options_to_sku["{$_option->getId()}"]["{$v->getData('option_type_id')}"] = $v->getData('sku');
    }
}
?>
    <?php endforeach; ?>
    </dl>
    <script type="text/javascript">
        var options_to_sku = <?php echo json_encode($options_to_sku);?>;

        $$('.product-custom-option').each(function(elm) {
            $(elm).observe('change', function() {
                var sku_suffix = '';
                $$('.product-custom-option').each(function(opt) {
                    if ($(opt).value.length==0) // no value selected
                        return;

                    var opt_id = $(opt).readAttribute('id').replace('select_','');

                    if (!!!options_to_sku[opt_id]) // no option values array found
                        return;

                    if (!!!options_to_sku[opt_id][$(opt).value]) // no sku found matching value id
                        return;

                    sku_suffix += '-' + options_to_sku[opt_id][$(opt).value]; // add to suffix
                });

                /**
                 * add here the code that adds the suffix to your SKU
                 */
                console.log(sku_suffix);
            });
        });
    </script>