Register Helper field type example shows an example of every possible field in Register Helper

rh_fields_example.php

<?php

/**
* This example is to show you the 'niche' options each Paid Memberships Pro - Register Helper Add-on field can take and how to use it.
* For more information on the Register Helper Add-on please visit https://www.paidmembershipspro.com/add-ons/free-add-ons/pmpro-register-helper-add-checkout-and-profile-fields/
**/

function my_pmprorh_init()
{
    //don't break if Register Helper is not loaded
    if(!function_exists("pmprorh_add_registration_field"))
    {
        return false;
    }
    //define the fields
    $fields = array();

    // TEXT FIELD
    $fields[] = new PMProRH_Field(
        "text_example",             // input name, will also be used as meta key
        "text",                    // type of field
        array(
            "size" => 20        // size attribute of text field
        )
    );

    // TEXTAREA
    $fields[] = new PMProRH_Field(
        "textarea_example",             // input name, will also be used as meta key
        "textarea",                    // type of field
        array(
            "rows" => 10,        // row attribute of textarea (height)
            "cols" => 50,       // cols attribute of textarea (width)
        )
    );

    // SELECT
    $fields[] = new PMProRH_Field(
        "select_example",             // input name, will also be used as meta key
        "select",                    // type of field
        array(
            "multiple" => true, //allow multiple selections for select
            "options" => array(
                "" => "",    // blank option to be displayed first, followed by options
                "option_1" => "Option 1",
                "option_2" => "Option 2",
                "option_3" => "Option 3",
            )
        )
    );

    // SELECT2
    $fields[] = new PMProRH_Field(
        "select_2_example",             // input name, will also be used as meta key
        "select2",                    // type of field
        array(
            "options" => array(
                "" => "",    // blank option to be displayed first, followed by options
                "option_1" => "Option 1",
                "option_2" => "Option 2",
                "option_3" => "Option 3",
            )
        )
    );

    // CHECKBOX
    $fields[] = new PMProRH_Field(
        "checkbox_example",             // input name, will also be used as meta key
        "checkbox",                    // type of field
        array(
            "text" => "Check this" // string for <label></label>       
        )
    );

    // RADIO
    $fields[] = new PMProRH_Field(
        "radio_example",             // input name, will also be used as meta key
        "radio",                    // type of field
        array(
           "options" => array(      // display the different options, no need for a "blank" option
                "option_1" => "Option 1",
                "option_2" => "Option 2",
                "option_3" => "Option 3",
            )    
        )
    );

    // FILE
    $fields[] = new PMProRH_Field(
        "file_example",             // input name, will also be used as meta key
        "file",                    // type of field
        array(
            "accept" => "image/*"   // accept all image types for file upload  (http://www.w3schools.com/TAGs/att_input_accept.asp)
        )
    );

    // HTML
    $fields[] = new PMProRH_Field(
        "html_example",             // input name, will also be used as meta key
        "html",                    // type of field
        array(
            "html" => "<p><u>Add a paragraph into your checkout.php for Paid Memberships Pro. You may also use normal HTML code to generate fields.</u></p>"   // accepts HTML code
        )
    );

    // HTML
    $fields[] = new PMProRH_Field(
        "hidden_example",             // input name, will also be used as meta key
        "hidden"                   // type of field - creates a field that is hidden. (Great for creating a honeypot for your checkout form)
    );


    /**
    *   Conditional field example. Display a textfield depending on checkbox value
    **/

    
    $fields[] = new PMProRH_Field(
        "conditional_example_depends_on",             // input name, will also be used as meta key
        "checkbox",                    // type of field
        array(
            "text" => "Check this to display a text field" // string for <label></label>       
        )
    );


    $fields[] = new PMProRH_Field(
        "conditional_example_show",             // input name, will also be used as meta key
        "text",                    // type of field
        array(
            "depends" => array(
                array(
                    "id" => "conditional_example_depends_on", //depends on this field
                    "value" => true //if checkbox is checked show this field
                )
            )
        )
    );

    foreach($fields as $field)
        pmprorh_add_registration_field(
            "checkout_boxes", // location on checkout page
            $field            // PMProRH_Field object
        );
    //that's it. see the PMPro Register Helper readme for more information and examples.
}
add_action("init", "my_pmprorh_init");

How do i make the below radio selection as required and how do i add the text box if user selects Option 3?

$fields[] = new PMProRH_Field(
"radio_example", // input name, will also be used as meta key
"radio", // type of field
array(
"options" => array( // display the different options, no need for a "blank" option
"option_1" => "Option 1",
"option_2" => "Option 2",
"option_3" => "Option 3",
)
)
);

$fields[] = new PMProRH_Field(
"radio_example", // input name, will also be used as meta key
"radio", // type of field
array(
"options" => array( // display the different options, no need for a "blank" option
"option_1" => "Option 1",
"option_2" => "Option 2",
"option_3" => "Option 3",
)
)
);

$fields[] = new PMProRH_Field(
"conditional_example_show", // input name, will also be used as meta key
"text", // type of field
array(
"depends" => array(
array(
"id" => "radio_example", //depends on this field
"value" => "option_3" //if checkbox is checked show this field
)
)
)
);

How can we pre-check a checkbox? Thanks