pilots are trained to land blind. The mistake was that that co-pilot was blinded also in this situation.
The child was allowed to take the controls, which is common practice when training anyone who doesn’t know how to fly. Again, the mistake wasn’t letting them take the controls, the mistake was made by the pilot who should have had his hands lightly touching the controls to ensure nothing unusual happened.
Not quite, depending upon what you mean by "blind". We are trained to land in Instrument Flight Regulations (IFR) and Precision Approach Radar (PAR) minimums. Further, depending upon the certifications the pilot is holding, they can be trained to 0/0 minimums which is a Special Instrument Rating meaning that they can takeoff and land in 0 miles visibility and 0' ceiling weather conditions.