Try this... before setup(), create an "infinite flag" and reset as "off"
int infinite = 0; // 0 = NOT infinite
Next, create a condition outside the button press tests "if the infinite flag is set... run your motors"
if (infinite) { // infinite flag was set... make the motors run
rotateMotor(4, 50, motorDir1); // Mode 1: 4 rotations, half speed
rotateMotor(4, 50, motorDir2); // Mode 1: 4 rotations, half speed in reverse (clockwise)
}
Then, if you press "button 1" you will need to turn the infinite flag "on" inside the "button 1" condition
infinite = 1;
Then, inside button "2", "3" and "5" you need to turn the infinite flag OFF so the "infinite" condition fails...
infinite = 0;