To make it sure,
I'll stay alone at the first night, but at the second night my filipino friend will stay with me overnight. Will you charge me extra or not in such a case?
No you can bring anybody to your room. And if somebody comes in without you, they will call you first to make sure you know the person.
no they will not but you can tell them your friend is coming the following day.
Get an answer from Hotel Royal Amsterdam staff and past guests.