It's not unfair. The main part of being in management is problem solving. If OP can't handle several of their boss' responsibilities or doesn't want to deal with them, then management might not be a good road to go down.

Taking credit for someone else's work doesn't sound fair to me.

life is unfair for everyone, therefore; it makes it fair for everyone.

Well OP has already won. This only proves that the manager is scared OP might get better than her and replace her or something. And the hard tasks will only make him better. It's just a matter of time before he is going to kick her ass.

Doing your job doesn't entitle you to a promotion, and it's indicated OP doesn't have all that management has to deal with under control anyhow. However, OP's moments of brilliance that his boss has been taking credit for will eventually be recognized. Proactive people aspiring for bigger things always find success somehow.

Except it's not OP's job, it's their manager's.... And if OP is doing managerial tasks, then he should be promoted to a position appropriate for those tasks and plus a wage that goes along with it.

Think about what you're suggesting for a second. An easy solution for the company is to "promote" OP to his boss' assistant, which would make less than a normal employee and would appropriately reflect OP's job. Relegating tasks to employees is nothing new, OP isn't entitled to a promotion over it. If he continues to show he's the better employee over his boss, then his company will see that.

your not listening 37, op is not being asked to do extra tasks that reflect their job position and expectations, they are asked to deal with manager issues which are not in their job description or responsabilities, because its something for higher ups who get paid more to do it, which eventually means OP should be paid to do so. you say they should not be paid more for doing their job, but its NOT their job. you should get paid for the job you do, not the position below you, otherwise you have a bad employer. that being said, we dont know if op will be promoted in the future, in that case they should embrace their "manager training"

That doesn't even make sense in this situation