Hi Vipul Thakur,
Thank you for reaching out to the Microsoft Q&A community.
I understand that you're incredibly in need of your BitLocker key. I wish I could share good news, but I have to be direct: no one can give you that, not even Microsoft.
The key is often saved to the very first Microsoft account used to set up the computer. If you have looked into every possible account but still can't find it at all, or it was never backed up, it is impossible to retrieve the key anywhere else.
At that point, the only way to get your laptop working again is to clean install Windows, which will clear all data and applications. To prevent the situation happens next time, you should save the key to multiple places, or you can turn BitLocker off in advance!
I know this is not the answer you were hoping for, and I'm sorry to have to share this difficult information. But I believe it is best to be direct and give you the correct information.
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