Is it possible to start the mobile without proper IMEI?

Question

In LTE network, there is no pattern for interface name such as X2, S1-AP, S11, S5/S8, Gx etc. But for the 5G network, it starts alphabet Nx where x denotes 1, 2, 3 as numeric. I could not get the logic behind this doing so. It may be some specific reason for that.
If anyone knows about the reason, please share. Thanks in advance.

Answer 1

Technologically there is partial limitation via the EIR but in the past operator used to bypass this varification and users was able to make a call without the IMEI number. Now various government had made is mandatory and you can not make/receive a call.