I want to join the below mentioned queries into single query
Is this what you need?

( SELECT ... )
UNION ALL
( SELECT ... )


The GROUP BY on the first SELECT seems to be useless; please explain why you have it.  I am less certain about the second query.

Not sargable: DATEDIFF(NOW(),update_date) &gt; 30; change to A.update_date &gt; CURDATE() - INTERVAL 20 DAY.

Recommend:

A:  INDEX(order_status, pending_order_type, update_date)
C:  INDEX(subscription_id, charge_amount)


When JOINing, please use FROM B JOIN C ON ... instead of FROM B, C WHERE ...

(If you need further discussion, pleas provide SHOW CREATE TABLE.)