At the end when they are looking at the checks, the camera is circling around the group and Hardison has the envelope in his hand. At the next camera cut, the envelope is nowhere to be seen and his arms are folded.
When Parker cuts a hole in the glass, she only cuts through a single layer. That exterior window would be a double-pane for insulation, so she would have to cut through two layers of glass. Also, the hydrofluoric acid she used would have produced toxic vapors that could have hurt her badly but she completely ignored them.
While watching Pierson's press conference on the CNN website, it's very obvious the web page is local mock-up instead of being from CNN.com. This is visible in the address bar of the browser.
In Hardison's flashback, the hotel manager and security are walking down the hallway to his room, with whoever was investigating the credit card fraud, and one of them says, "Break it down!" At least one of them would have a key, since one or two of them are hotel employees. It makes for a funny action sequence, but there's no reason to break down the door.
Parker mentions that the guards had been "ganked" after Elliott knocked them out. "Gank" is a slang combination term for "gang kill", so since the guards were not killed, this use was inaccurate.