Hello TamoorSohail,
My name is Raymond, welcome to Microsoft I am a Microsoft user just like you.
I hope you are doing well.
I understand you are inquiry is about not being able to login as admin to Microsoft 365 Developer Program after you changed your email address to your primary email.
This issue may require account access and this is Microsoft community and we do not have access to your account.
To best resolve this issue, please contact Microsoft support.
Kindly go to Microsoft Contact Us website: https://support.microsoft.com/contactus/
Type the issue and click Get Help.
Click Login and Contact Support at the bottom of the page.
Log in with your Microsoft account. Select appropriate prompt & Click "Chat with a support agent".
Or find link attached to chat with support:
http://Support.office.com/home/chat
Please try these steps I have provided and let me know if you need more assistance.
Give back to the Community, Help the next person who has this issue by indicating if this reply solved your problem. Click Yes or No below.
Warm Regards