Unfortunately, Microsoft Support cannot retrieve, generate, or bypass a lost BitLocker recovery key, as the key is not accessible to support representatives.
When you mention changing your account security information, are you currently receiving a message indicating that the changes will take 30 days? if you cannot access your Microsoft account because a security information replacement is pending, Microsoft normally requires a 30-day waiting period, which support cannot accelerate. In the meantime, consider whether another Microsoft account was previously used to configure the laptop, as the BitLocker key might have been saved under that account. You can also check for any previously saved recovery key files or printed copies. https://support.microsoft.com/windows/security/encryption/find-your-bitlocker-recovery-key.
Regarding your USB installation media not being recognized, could you please provide your laptop's manufacturer and exact model, and clarify whether the USB drive is missing from the BIOS/UEFI boot menu or whether Windows Setup starts but cannot detect the internal drive? These situations require different troubleshooting procedures.
Please avoid formatting or deleting partitions for now, as reinstalling Windows without unlocking the BitLocker-encrypted drive could permanently erase your existing files.