Is learning assembly programming language important for making operating system?
Yes, if you want to program microcontrollers or if you want to get the maximum speed of your CPU or if you want to code some special timecritical drivers or if you want to hurt your brain and get insane.
It highly depends on your workings .In your work if you have to go in deep level about the workings of computer then you have to learn it .Most often you don't. https://www.codeproject.com/Articles/89460/Why-Learn-Assembly-Language#:~:text=Assembly%20language%20gives%20you%20complete,to%20retrieve%20values%20or%20pointers
Depends on what you wanna do, it's a very low level programming language which makes it harder than C++ to learn, it's mainly used for hacking, hardwares and browser development
Not so, But if you are interested in computer understandable language then you can proceed to learn it.
To my mind no. You can use c,c++,python