1: V1= last chance to stop, Minimum speed to go
VR = Speed for initiating rotation
V2 = basically minimum safe climb speed
2: as a back up to you looking at the airspeed indicator.
3: depends very much upon the airline. Generally you can add "positive climb" at which point the gear is raised. Most airlines will also have a call at "80knots" or "100knots" as a chance to check that both airspeed indicators are working correctly. Approach calls to numerous to go into, really.