Tested this movement (inside assigned NIC in section IPConfiguration, there is an option to change subnet, which restarted VM). After restart VM had new private IP from different subnet. I also tried to stop VM in subnet, where only this VM was assigned. Then I tried to create new AppGtw to this subnet and portal did not give me the option, selected subnet was not possible to use. Even if VM was stopped, it still had its privateID (public was released) what was probably the reason, why this subnet is not usable for AppGtw.