This scenario is well discussed in this forum. The answer is that according to the Bonvoy T&Cs, you must pay *and* stay at the hotel in order to get the qualifying points and nights. You will always run the risk of the hotel discovering that you are not actually staying even though you've checked in and paid for the room and you could feel that what you do with that room is up to you but you will run the risk of the hotel not posting the nights and there will be nothing you can do to complain about it. Usually, if people are doing this type of thing then they do it at a hotel near home where they can check in, mess up the bed, leave and maybe go back a few times to mess up towels and finally check out at the end. Obviously this won't work if your chosen hotel is in a different country and you fly there specifically to check in and then fly home.

For 12 nights, I'd say your plan is too risky and I'd consider another way to get the 12 nights. Maybe find a more local hotel that you can do six weekend breaks in without the risk of breaking the Bonvoy T&Cs.

Your plan to get the 12 nights to become Lifetime Platinum is worth the investment in my opinion. The alternative is that you will have to do 50 nights in another, future, year and this will be more challenging and costly than biting the bullet on 12 "mattress run" nights this year and being done with it.