Problem 49: Mr. Oswald's phone

Mr. Oswald forgot the pass lock pattern on his mobile phone. He remembers that the pattern starts from the dot labeled A, and ends on the dot that is labeled B. The pattern is made by 4 strikes.

He decides to unlock his phone by trying some patterns. However after 5 wrong patterns the phone will be disabled for 5 minutes.

i.          How many different pattern can be drawn from A to B with 4 strikes?

ii.          What is the probability that he can unlock his phone without disabling it?

A pattern example is drawn on the phone image above.