Cardinals are not allowed to take cellphones into the conclave. And even if they did smuggle them in the phones would be useless. During the conclave there is a special dampening field around the Vatican which makes it impossible to use cells.
During the conclave the Vatican is crowded with pilgrims and journalists from all over the world. There would be enormous amounts of people everywhere around St. Peter's Square and the safety regulations are extremely high. It would be impossible for the nuns to enter the center of the Vatican with so much ease.
Bishops don't participate in the conclave and they don't discuss possible choices with cardinals as was shown here.
The conclave takes place in the Sistine Chapel. The shown interiors look nothing like the original Chapel with the famous fresco "The Last Judgement" painted by Michelangelo.
Around 13:51 (13 minutes, 51 seconds), Crimson can be seen loading an arrow into a crossbow. However, she places the arrow on top of the string without ever drawing it back. The arrow would never have been able to be fired.
The oath before the voting is spoken in Latin (and not Italian like Duretti did) and goes like this: Testor Christum Dominum, qui me iudicaturus est, me eum eligere, quem secundum Deum iudico eligi debere.
A nun would bless a child by making the sign of the cross on its forehead and not like Ava.