It basically means, "you shouldn't be pointing out that particular error of mine, when you have also done the same thing or worse." It's what you might say to a hypocrite.

I think many English speakers probably don't even know the difference :) As I understand them, litigation is something you might do within a lawsuit. Or the act of bringing a lawsuit against someone. "Litigation" is a verb, and "Lawsuit" is a noun.

"The words of the reckless pierce like swords, but the tongue of the wise brings healing." Proverbs 12:18 (NIV Bible) "He who guards his mouth and his tongue, Guards his soul from troubles." Proverbs 21:23 (NASB Bible) :)

Yes it is correct, but it would not be a very polite way of saying it. "Fetch" is a word used when dogs retrieve sticks. (The owner throws a stick and the dog "fetches" it). So it is not necessarily a word you'd want to use when directed at another person — unless with friends in a very informal, joking sort of way. OR could be something a King or Queen would say to his/her servants. Along those lines :)

Yes it can mean those things, but can also mean "important." (Probably most often means "important.") But it does indeed depend largely on context.

The more correct sounding to me would be: "How much do you weigh?" Or "What is your weight" "Weight" is a noun, whereas "weigh" is a verb, (I believe (?)$. So you would phrase the questions differently. Although I think most English speakers would completely understand and not question your original sentence.

Yes, they are different. The first is implying the possibility of a present condition ("could be") and the second is implying the possibility of a past condition ("could have been"). Example: "Why does that woman look so confused? She could be lost." (notice that "does" is present tense) VS "Why did that woman look so confused? She could have been lost." (notice that "did" is past tense) Hope that helps!