Yes, you can upgrade to Windows 10 from a fresh Windows 8.1 installation.
Yes, you can upgrade to Windows 10 from a fresh Windows 8.1 installation.
It seems unlikely you could purchase Windows 8.1 and upgrade directly to Windows 10 at the same time. Windows versions are generally not interchangeable, and upgrading from one to another usually requires purchasing the newer version outright. However, prices in Finland might make it more affordable to buy Windows 8.1 now and then upgrade later if needed.