Very slightly damp cloth, I wouldn’t use any product.
I used glasses cleaning wipes, took the anti reflective coating of my MacBook screen. Luckily even though my laptop was over 5 years old Apple replaced it free of charge. Now I just use a slightly damp cloth.
I don’t know, I’ve never used anything other than a slightly damp cloth.
Recently read this is the only way too.
On the topic of cleaning, what about the keyboard? Even regularly washing hands the keyboard gets very greasy and I have to wash it every day with wipes. Recently purchased a slim 'cover' that goes over the keyboard and seems to be doing the trick only downside is the resistance of the keys are much increased and doesn't feel as good to type on... I never found a way to 'lock' the keyboard either.... and turning the macbook off soon as you press any key it turns on...