Hi Suresh,
Thank you for reaching out to us. I see that you would like to be whitelisted for BudgetOrderService. Could you please provide me the highest MCC ID needed to be whitelisted that is appropriate for your use case? For privacy, you can click "Reply Privately to the Author".
For the other query, unfortunately you cannot make a customer account into a manager account. However, you can create a new manager account and
link the new manager account under the old manager account if this is what you need. Let me know if you have further questions.
Thank you,
Bryan, Google Ads API Team

ref:_00D1U1174p._5001UXVLP4:ref