You can upgrade your windows from 7,8.1 to Windows 10
Do not forget to check for the system requirements, especially your graphics card.
You might face some technical issue with your computer such as; Display, printer & Scanner, Drivers, documents disappear, online gaming, other applications will not support due to compatibility issues.
No need to worry to avoid such scenarios, we do have a Roll back option i.e. downgrading the Operating System (Windows 10 to Windows 7) .
Before you proceed you need to take a backup of your important files and data.
Enjoy Windows 10.