BuddyPress.org

The groups_unban_member hook fires before the unbanning of a member from a group and the the groups_ban_member hook fires before the banning of a member from a group.

Both hooks are defined in the bp-groups/bp-groups-functions.php file.

Maybe this part of the BuddyPress Codex could help you:

Change Default Members Profile Landing Tab

Try this:

add_filter( 'bp_members_signup_error_message', 'function_voornaam', 10, 2 );
function function_voornaam( $value, $fieldname ) {
if ( $fieldname == 'field_1' ) {
return '<style>{font-family:bold}</style> you have to enter name.';
}

return $value;
}

function hide_friend_tabs_for_other_users() {
if ( bp_is_user() && !bp_is_my_profile() ) {
bp_core_remove_nav_item( 'friends' );
bp_core_remove_subnav_item( 'activity', 'friends' );
}
}
add_action( 'bp_setup_nav', 'hide_friend_tabs_for_other_users', 10 );

Migrate from what? Do you use another community/membership plugin at the moment?

You can create a subdomain and set up a WordPress website there