How can i remove required field validation on click submit button?
In the form_alter function you can use the limit_validation_errors property. 

'#limit_validation_errors' =&gt; array(),


The above code will not perform any field validations. You can then add the individual fields that you need to validate here using the below code.

$form['actions']['next']['#limit_validation_errors'][] = array($field_key);


Where next is the action that I am using.