lever climb to flash you need THR RED altitude. It cannot happen at in cruise phase.
Oh yes it can. DSC-22_30-100 "B"
LVR CLB flashing white - Request to set the thrust levers in CL detent in the case not in position while the aircraft is above the altitude of thrust reduction with both engines running.
Whenever the A/THR is armed and the TLs are not in the CLB detent, you'd get told by the aircraft they're not where expected. The first instance is passing ACC ALT in after take-off, indeed.