You may acquire good skills on IO commands by practising experiments given in the following link: Practising IO Commands
No!We have omitted the CLR to save space in the breadboard with a little bit risk. But, as the display system is a multiplexed ( after adding DP1 - DP3) type one; hopefully, the average current would remain below IOH.
(But, the rule of language says that people infer the relevant meaning of word as the context dictates. We are playing with 7-segment display devices; why should we think that cc could mean 'cold cathode' of a triode instead of 'common cathode pin' of a 7-segment display?)
"Hopefully", the student's code won't freeze mid-loop, and screw-up the average current calculation, to the detriment of the Arduino's output transistors.