Yes. A Windows 10 license key works for both architectures on the same device.
Right-click Start → System → Look under "System type". windows 10 32-bit free download
No. You must perform a clean installation and wipe the drive. You cannot "upgrade" the architecture. windows 10 32-bit free download
Is Windows 10 32-bit really free? The short answer is: The download is free, but a license is required for full activation. windows 10 32-bit free download