Answer:
Yes, we can boot a computer and load the operating system without using any type permanent storage device. When a computer capacity get loaded in the storage device then, it search for the operating system. So, this can be skipped by using the bootable device like USB.
In the operating system, it is mandatory to have USB whenever the computer boots as it helps to boots the overall operating system. As,we cannot store this in external USB because it is very risky for the system and sometimes lead to damaged the system.