This all assumes that the aircraft is turbojet/turbofan powered...
some turbopropellor types as well.
With older turboprops, and all large piston powered transport aircraft, V2 was achieved
before liftoff...ie: the takeoff rotation was started
at V2.
When jet transports came along, this was found to be impractical, as many of the early types (B707/DC8) had no/minimal leading edge devices, which required rather high V2 speeds...with resultant runway length/tire limit speed problems.
Having personally had takeoff runs approaching 12,000 feet in early model 707's, the idea of continuing to V2 before liftoff was
not appealing, as in...up close and personal with the weeds at the end.
And that was with all
four turning.
