wealthy

Check this

http://www.paidmembershipspro.com/hook/pmpro_currencies/

if you look in Githhub there is some code you can use do restrict spaces

strangerstudios/paid-memberships-pro

or there is this code that Might help

// Restrict username registration to alphanumerics
function limit_username_alphanumerics ($continue_registration) {

    global $username;

    if (! preg_match('/^[A-Za-z0-9]{3,16}$/', $username) ){
        pmpro_setMessage(__("Username can only contain alphanumerics (A-Z 0-9)", "pmpro"), "pmpro_error");
        $pmpro_error_fields[] = "username";
        $continue_registration = false;
    }

    return $continue_registration;
}
add_filter('pmpro_registration_checks', 'limit_username_alphanumerics');

How are you trying to restrict levels BCD ?
Does each level give them different access and or time??

Can you please explain what you are wanting to strict?

Each level , no matter what you give it in access, is all controlled at the pages.
So if you put a tick on a page ( right sidebar) for level B only, then anyone signing up for A, C and D wont see this.

or give it multiple ticks for A,B and C and then only D wont see that page.

Does this help??

look at the Banned Users tab..
2 down and first box.. ( on settings screen

So did the other plugins send mail? Like your contact page..
(making sure it is the same email address and that also the email is not hard coded into the contact form.)

The PMPro mail is sent to the default email setup in the “Memberships Email Settings” area.
also test the Only Filter PMPro Emails?: by putting in the tick and removing it. ( save between each)
also tick the Send the site admin emails: settings

If you are going to edit any files, you should put these in your child theme. that way these will be used rather than the original files.

and when the plugin is updated, they wont get over written.

so put the file in the same folder (structure) within your child theme.
So in this case create a folder /paid-memberships-pro/shortcodes/ in the child theme and put a copy of that file in there and then modify that file.

A child theme is a theme that inherits the functionality of another theme, called the parent theme. Child themes allow you to modify, or add to the functionality of that parent theme. A child theme is the best, safest, and easiest way to modify an existing theme, whether you want to make a few tiny changes or extensive changes. Instead of modifying the theme files directly, you can create a child theme and override within.