I'll try to answer as best as I can.
We're talking Windows 10 here,
1 Macrium free is better to create images than Windows' own backup program. click here.
2 No installation disks but Windows 10 offers a 'refresh' of the OS where you can choose to keep files and folders or keep nothing which means a new install.
3 Windows 10 firewall is fine. I run Defender and Malwarebytes Pro with CryptoBlocker and AntiWebMiner.
Most here also use the free version of Crapcleaner to maintain their computer.