How to install windows 10 in HDD while Ubuntu is running in SSD?

I am using ASUS FX553VD laptop with ~256GB SSD and 1 TB HDD. In SSD Ubuntu 18.04 is running. and that HDD is free.

So, I want to install Windows 10 in HDD. Is it possible ? And if it is, then should I remove my SSD first while installing Winows 10 ?

Fine. Suppose I did as I mention. Now I installed my SSD again. So,

1. what will happens while on boot ? Which OS will running fine ?
2. If I want to run both OS smoothly then what are the ways or steps I should follow during installation of windows.

Actually I want to play some games on windows during this lockdown period. Thanks in advanced.

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