Does resetting Pavilion dv6 to factory settings also reset any BIOS changes made in the past, setting them back to default?

I purchased a used (old) Pavilion dv6 laptop that was running Windows 10. The seller set it to revert to factory settings to remove all of his data and programs, which also changed Windows back to Win 7. I have reinstalled Win 10 from a thumb drive. Did the factory reset also change the CMOS/BIOS settings back to default settings too (if changes have ever been made)? I noticed the windows system time is randomly changing on me, and I wondered if it's possible the CMOS battery is weak, and may be the problem. If I replace the CMOS battery (with all power off), do you think I will have any probl

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