Hello Ashwin,
Welcome to Microsoft Q&A forum. It's my pleasure to help you today.
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I understand how frustrating it can be when your account restriction is preventing you from download app, especially when it is hinder your business.
An individual Microsoft account age is set as the time of creation. Change to the date of birth later might not be applied due to the reasons that actual children might abuse this as a loophole to dodge parental control.
May I know if you have made any purchase on this account yet? As I know, purchase on child account will need approval from an adult account. If you haven't bought any subscription or license yet. You can go to account.microsoft.com to change the log in email. Then you can remove the current Gmail account and use it to create a new one.
If you have bought a subscription, you can work around it by creating a new adult account. Add the current account to the family group and remove all restriction, this way you can freely access and download all the application.
This is a public forum, to moderators have limited access and cannot access your account to check for you. If you require more support, please contact Microsoft live support to see if there are any way they can help you verify your correct age.
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