The absence at the current moment (October 25, 2021) of new powerful solar flares allows us to once again draw attention to the significant events of the past 24th solar cycle. These certainly include a pair of X5.4 and X1.3 flares on March 7, 2012, which occurred in the same active region with a delay of about one hour. They were accompanied by prolonged (more than 18 hours) >100 MeV γ-radiation. Each of this pair was accompanied by its own fast coronal mass ejection (CME) >1800 km/s. The X1.3 flare is notable for small changes in the intensity of soft X-ray radiation (SXR), temperature and emission measure of the emitting plasma, despite the intensity of the hard X-ray radiation (HXR) at maximum comparable to that in the flare X5.4. An analysis of the observations shows: 1) the larger X-ray class X5.4 of the first flare is associated with chromospheric evaporation into low coronal loops; 2) the absence of the observed chromospheric evaporation in the second flare X1.3 can be explained by the presence of only high coronal loops left after the first flare; 3) in both flares, the main acceleration of the CME occurred up to the maxima of the HXR bursts; 4) in both flares, relativistic electrons and protons were accelerated stochastically at the post-eruptive phase.