Верно ли выражены просьбы (can, could, may)? Can you give me

1. Can you give me your book? We can also use could to make this request more polite. 

2. Can you bring me some tea, please? This is an informal request. If you want to make it more formal and polite, use could. Could you bring me some tea? 

May I come in, please?

Could you help me with this task? A formal, polite request. You can also use can to make it less formal. 

Could I go to the party, mum? Could is usually used for formal requests, it is more natural to use can in this context. 

Can we meet later? 

May I ask you a question?

In general, the choice of can and could depends on the context. You should remember that could is more polite than can.