Continuity mistake: When going to the Gotham City Bank, the clock tower bell will begin to ring. Alfred then contacts Batman and says that it's now 12:00 AM and wishes him a merry Christmas. If you look at the clock tower, however, the clock says that it's only 9 o'clock.
Continuity mistake: Batman uses gadgets in Origins he doesn't get until Arkham City.
Continuity mistake: In the Batcave, when Alfred is telling Batman that he is a man, not an island at the end, Batman's cape is nowhere near him. In the next shot, it's on his back. The back of his mask also inexplicably appears as well.
Answer: 1. There could be any number of reasons but the most highly likely one is that he wants Batman to see the face of the man who would beat him. 2. The TN-1 drug is a more powerful version of the strength enhancing drug Venom. Since Batman has shown to be quite a capable fighter, Bane had it with him and used it during his fight with Batman as a last resort to kill him.