How to correct errors in hearing order?

Just file the application under Sec - 151 CPC  to let the court correct the order.

if there is an error in the ordersheet of your case, you can file an application to recall/correct the order within 30 days under Order 47 Rule 1 of the Civil Procedure Code. It is advisable to file the application as soon as possible and serve a copy to all parties in the case.

Adding additional party as a party in the case, and withdrawal of case are two different distinct matters. Better to clarify the order first from the court itself.

To amend judgement ,decree ,orders 152 s of CPC.

I am of the view that this is minor mistakes of inconsequential import with mere possibility of two views on the subject, that is adding party or for the withdrawal of the case. 

Bring to knowledge of court ,court will rectify it.

Since next  hearing is more then 30 days how to approach court? Should we just file application with registrar?

You can file an IA for hearing advance to advance the hearing from the next date to current date with an affidavit explaining and affirming the reasons that you rely upon to advance the hearing date.