Just add friend as the 'named second guest' on the room reservation at the time you book, making sure you book as 2x people room or you don't get the option you need. Each hotel is run as a franchise, some franchises don't care about this, whilst others do.

Account shutdown is only likely for extreme abuse, like profitting by selling / charging the elite room upgrade to your friend.
Most likely is hotel notices and either doesn't care, so you get points, or cares and reception decides to not credit you any stay points.
It costs hotels real money to buy those points from IHG that they give you, and your friend has already obtained unentitled financial benefits of eg room upgrade.

T+C's say if elite doesn't stay, there is no bennies entitlement, room upgrade / free internet etc. In practise your friend checks in first, gets upgraded room, and keeps even if you do not appear later. It is the other bennies that could get charged upon checkout to your friend if you are not there, eg free internet, free movie, free minibar, free lounge etc.

On checkout, result depends on if franchise cares or not. Easiest for you and your friend, is just have your friend leave and allow hotel to complete checkout in your/their absence and charge extras to cc used to reserve room.

Ssome countries require id of all guests in the rooms, eg Italy, Thailand to name two. If no country ID requirement, then you have a better chance of getting the result you want.

As RA, I have occaisionally book an IC room for family/friend(s) on their birthday or similar celebration. I have always asked hotel, and each time my friends got a 1-level immediate room upgrade, and maybe extra level upgrade at checkin if rooms were free However always it was mentioned by hotel, that my booking has ..no free lounge, no free mini-bar, no qualifying nights/points as I was not using the room. For me being open and honest upfront got good results.