Law 24.3 states: "A ball is fairly delivered in respect to the arm if, once the bowler's arm has reached the level of the shoulder in the delivery swing, the elbow joint is not straightened partially or completely from that point until the ball has left the hand.
Running up does add some speed to the ball.
Bowling speed = 130 km/h
Running speed + 15 km/h
=> Total speed = 145 km/h
The spin is different as well. While standing a bowler just has a circular movement based on their arm length. Running up causes that movement to be elliptical.
This isn't all, though. There's also velocity, ...
This is called a short run. Quoting from Law 18:
18.3 Short runs
18.3.1 A run is short if a batsman fails to make good his/her ground in turning for a further run.
18.3.2 Although a short run shortens the succeeding one, the latter if completed shall not be regarded as short. A striker setting off for the first run from in front of the popping crease may ...
Quoting from Law 5, The Bat:
5.7 Bat size limits
5.7.1 The overall length of the bat, when the lower portion of the handle is inserted, shall not be more than 38 in/96.52 cm.
5.7.2 The blade of the bat shall not exceed the following dimensions:
Width: 4.25in / 10.8 cm
Depth: 2.64in / 6.7 cm
Edges: 1.56in / 4.0cm.
Furthermore, it should also be able to pass ...