Removing lock screen in Honor 5X

We bought this Honor 5X in Jun 2016 to replace my wife's aging Sony xperia R. It was more than 2 years old and was getting very slow. This 5x has served my wife well for about 2 years and couple of months. Then she started experiencing slowdowns since her use of phone for translations etc is heavy. 

So about six months ago, wife upgraded to Redmi Note 7 Pro with 4GB ram and its working well. Since she ditched this phone, I am using this as my main device since it's better than my then in use Panasonic T45. 

Now I'm getting a new phone as gift, and while getting it, I have decided to exchange this Honor 5X with that. I'm getting about INR1600 ($21) for this in exchange. Considering the target device is INR11450 ($153), it's good bargain. 

One condition for exchange is that you have to disable the locks in the device being given in. So I tried for couple of days to get rid of the PIN lock I have ben using. But the "none" option would stay grayed out and would display something like this beside it: "Disabled by Administrator, or security policy etc etc". I had faced similar issue with other phones. So I cleared out credential Storage, removed apps having admin access, and tried couple more things. 

Then on a Reddit thread I got a solution. It's a bit crazy: Set pattern lock with backup pin. Then lock the phone. And on unlock screen enter some (usually 5) wrong patterns. Then enter backup pin. Then all locks are removed. 

First time I tried, it did not work. I mean backup pin button was visible, but could not be pressed. Anyway I tried again, and this tine it worked. Pretty convoluted, but now the locks are truly gone. 

Cheers!!!