As it is said, “You shall be plucked, etc. This prophecy was said regarding the exile of Bavel.

It is not concealed, etc. You might ask that in parshas Va’eira (Shmos 8:18), Rashi comments on the verse והפלתי (I will set apart) that it is an expression that connotes separation [and he then adds, support from our verse], “It is not נפלאת (separate) from You, etc.” But here Rashi explains that it is an expression of concealment. Re”m already answered this question in parshas Shoftim (above 17:8) on the verse If a matter of law is too abstruse (יפלא), [where] Rashi explains that הפלאה always denotes separation, or setting apart, etc. See there.

For if it were in heaven, etc. Rashi is answering the question: The beginning of the verse and the end of the verse apparently contradict each other. At the beginning it is written, It is not in heaven, [for you] to say, ‘Who will go up to heaven for us, etc.’ This implies: [that it is not in heaven], but near enough to send a messenger for it. It [also] implies that it is not that close that you do not [even] need to send a messenger for it. But afterwards it is written, For the matter is extremely close to you, etc., implying that one does not even need a messenger. Therefore Rashi explains, 'It is not in heaven,' (For if it were in heaven, you would be required to ascend in quest of it). But if it were in heaven it would be impossible to send a messenger after it and if you wanted to study it, you yourself would have to go up for it. Therefore there is no [longer] a problem when it is written [afterwards], For the matter is extremely close to you, [because the beginning of the verse too, is talking about the person himself and now it is saying that, on the contrary, it is close to the person himself]. And when the verse says “[Who will go up to heaven for us], and acquire it for us, [which implies that we are dealing with a messenger], it is adding even more, that [you might mistakenly think that] not only could you certainly never travel or go up to study it there, but you would never find any person to go up or travel [over the sea] in order to bring so as to study it.

The Torah was presented to you in written and oral form. Rashi is answering the question: Even when the Torah is in front of us it is difficult to understand because of the depth of the subject matter and the shortcoming of the one studying it! Regarding this he explains, The Torah was presented (to you) in written and oral form, and therefore the understanding of the written Torah is very plausible [if one studies it] in conjunction with the Oral Torah.

If you act with goodness, then you have life, etc. Rashi is answering the question: The verse should have mentioned each thing and its opposite, life and death, and good and bad, as it does below (v. 19). Furthermore, See, I have placed before you, etc. implies that man's acts of goodness are in Hashem's hand, but this is not so because they say (Megilla 25a), Everything is in the hand of Heaven except for fear of Heaven. Therefore Rashi explains, “One hinges on the other — If you act, etc. meaning that if on your account do good, etc., I will give you life, but if on your own you do bad, I will give you death. Because it in your hands to choose of the good or of the bad, and you choose from whichever you want.

So that when evil befalls you, etc. Rashi wants to answer: They had not yet done anything [bad], so for what could they be invoked as witnesses? He explains, So that when evil befalls you, etc. I.e., they serve as witnesses to Hashem's warning.

Another interpretation of “I invoke as witnesses, etc. The Holy One, may He be blessed, said,” etc. Because according to first interpretation you might ask that it should have said, I warn you before heaven and earth, because they are to serve as witnesses to the warning. Therefore he says, Another interpretation, etc. And according to the other interpretation you might ask why the verse says העדותי which is an expression that denotes testimony or warning. Therefore he also says the first interpretation.