They say they only want to be friends, then they try to make you break up with your partner because they want to be in a relationship with you. Why pretend to only want to be friends?
They give you something, say no strings attached but then at a later point, maybe a few weeks later or even months, they want you to do something because of the thing they gave you. Why say no strings attached if you expect a return?
You ask them if they want to go out to do anything and they say they're busy while they just don't want to do that. Why can't they just say they don't feel like going out or doing that thing?