Englishal
The question was when is LIFT greatest, not LIFT COEFFICIENT (CL) which you are getting confused with
Also you say <but then this will be a pointless question as the 'amount of lift (in Kg)' will increase with airspeed indeffinitely (theoretically)>
In straight&level flight, lift always=weight. As speed increases, the pilot decreases the aoa therefore decreasing CL - lift stays the same unless the weight changes
Lift=1/2*CL*density*vsquared
rubik 101
At rotation, you are still on the ground as the nosewheel lifts.
Therefore the weight is supported by the wheels. Think of a see-saw. Lift is not doing anything, in fact due to tailplane downforce, there can be more force on the wheels during rotate than when the nosewheel is on the ground.
At unstick, if that is what you mean, there is a considerable vertical component of thrust assisting lift, as I explained above, therefore lift is not at the maximum for that weight.
(eg if you rotate to 20degrees and assume the thrust is parallel to the a/c axis, the vertical component of thrust is sin20 which according to my trusty casio is 0.342 - so over a third of the upward force is provided by the engines!)
The correct answer stands as per Tinstaafl's post.