If you flip a coin twice. Event A is getting a head on the second flip and event B is getting a head on the first flip.

So, what's your question?

The probability of getting a head on the first flip is 1/2. The probability of getting a head on the second flip is also 1/2. The second event is independent of the first event (it doesn't matter what you flipped the first time and vice-versa).

The probability of getting two heads is 1/2 x 1/2 = 1/4. The probability of getting two tails is the same.
The probability of getting one head and one tail in two throws is 1/2.