Selecting text

1) On any webpage you can. The apps, it depends if the developer implemented the copy and paste and select and/or depending on how they display the content.
2) I just double tap the word I want to highlight if it is something I'm working on (meaning text message, email or notes, etc) or if it is static (webpage or something) I usually double tap but on the second tap hold to make sure it knows I want to select it. Just my way of making sure it knows what I want.