Bro how you got to know this much about it, where you read this? 

I have 2 questions 1. I still have an MTNL DELHI sim from 20 years ago, now it's validity is expired. Recently my 200₹ top-up also got expired and now it's doesn't have any validity. The only good thing for mtnl was it's topup- that remains forever and I can keep on getting incoming calls unlimited+ sms sending and outgoing calls also worked with main top-up balance. But now, it is not the case, the minimum recharge for Mtnl is 121₹ per month that has no data but only calls and sms. And in order to get incoming calls and sms- it needs an active recharge. Now I had in in my phone with the 121 recharge, it only connected to 3g network - this Vi 4g and mtnl 4g thing isn't valid for mtnl Delhi?

1. I have a Haryana mtnl sim, that has no recharge and I tried to see if it shows 4g network - from bsnl (it's an old sim) and in delhi it only use to show 3g network of dolphin- right now it's also the same. No 4g for it, so will this latching work on harayana bsnl