What does "Oh, please" mean?

Is it okay using "blown" without "up" to say "spoil something"? To be precise, shouldn't it suppose to be "blow up"?

No, it does not need to be "blow up." It is okay to use "blown" without using "up" after it. This is because "blown" and "blown up" have different meanings. In this case, it means to ruin. When she says that he could have blown months of work, she is saying that he could have ruined the case and all of the work that was done. "Blown up" or "blow up" has a different meaning; it means to destroy something with an explosion. Here are examples of "blown" being used in the same context. Ex: He could have blown the entire operation! Ex: I blew it. I can't believe I ruined the surprise.

What's the difference between "tool" and "equipment"?

In the general sense, a tool is an object or thing used to achieve some purpose. For example, a screwdriver is a tool used to secure something in place. Equipment generally refers to a set (multiple) of tools used to achieve a purpose. For example, screwdrivers, hammers, nails, and so on can be considered a set of construction equipment. Ex: I bought some gardening tools recently. Ex: I don't have my sewing equipment with me, so I won't be able to help mend your clothing.

What is "the powder room"?

A powder room is similar to a bathroom, but it lacks a bathtub or shower. Powder rooms have a sink and toilet like most bathrooms/washrooms have, so it's sometimes called a "half bath" or "guest bathroom." It's a place where people can "freshen up" (i.e. tidy up or put on makeup), so it was called a "powder room" in the past. Now, many people prefer to call them half baths instead. Ex: A: Katie, where's your washroom? B: There's a guest bath down the hall! Ex: This house has two bathrooms and one half bath.

What is skipped in front of this sentence?

"Do you" is left out at the beginning of the sentence. The sentence should be "Do you want some?" During informal conversations, you may notice that words are left out of sentences. This is because the remainder of the sentence can stand alone and is perfectly clear without the help of other words. Words that are commonly left out are helping verbs, articles, possessives, and personal pronouns. Ex: (Do you) Know where it is? A: How's Annie? B:(She is) Not feeling well. A: How are you? B: (I am) Doing well. Ex: (Are) You ready?

What does "hair get flat" mean? Does it mean the hair to be squashed or get greasy?

"Hair gets flat" means it lost its volume and lies close to your head and face. Ex: My hair gets flat every time I wear a hat.