Unable to implement Register button through either K2, Community Builder, or default Login Form that comes with Joomla. Is there a URL for register button which I can then add to website (tnssecurities.in) by custom HTML option?
First, you have to create a Menu item to allow a convenient access to Users Manager / Registration Form. Let's say, you create an Url likes this one:
index.php?option=com_users&view=registration&Itemid=999
Secondly, you can call this Url from any component and it will give users access to registration form.
Finally, in a "Custom HTML module", Urls will be automatically translated to its SEF representation. To generate a SEF Url from a view, you have to call:
<?php
echo JRoute::_('index.php?option=com_users&view=registration&Itemid=999');
?>