You’re correct that you would use “whose” to talk about a company. English doesn’t have a possessive form of “that.”

Here’s a link to a show I did about “who” versus “that.” It’s mostly about how you shouldn’t use “that” to refer to people, but there is a short section about using “whose” to refer to inanimate objects: http://is.gd/Qqg

“Which” versus “that” is a very common question.

The general rule is to use “that” for restrictive clauses (clauses that change the meaning of a sentence) and “which” for non-restrictive clauses (clauses that don’t change the meaning of the sentence).

Here’s a link to a show I did about this topic: http://is.gd/QpZ

“i.e.” and “e.g.” are abbreviations for Latin terms.

“I.e.” means “for example, and “i.e.” roughly means “in other words” or “in essence.”

For more details you can see the show I did about the topic last year: http://grammar.quickanddirtytips.com/ie-eg-oh-my.aspx