gr8shandini
Everything you write, along with Lemurian, is indisputable. However, you are also not fully taking in the definition of Coffin Corner. You both describe manouvers that pull you back from the precipice. Reducing power inside the box causes a Stall, which is the A/C's honest response to lost lift; it wants to gain speed and refly. But you are at Vne, so the Stall becomes disastrous. Likewise, if you alter Pitch up or down you tumble out of control. BOAC said it best: it is a "one way street".
best, Airfoil