Time phrases problem

There are four questions I'd like to pose.

1. I know the difference between "last year" and "in the last year" - the first meaning the year before this year, and the second meaning roughly "from 365 days ago until now". I also know that we use the perfect tense only with the second clause. But does that mean that we can also use the present perfect tense with other time periods like "in the last two/three/ten years" or "in the last two months"?

2. If I'm talking about a week immediately following the week that includes "today", I don't put any article before that phrase, right?

I'll phone you next week.

But when I'm talking about a week following any other week, "the" should be included, is that right?

Well, the week of January 4 won't work for me, but we can go shopping the next week.

If so, shouldn't I write "in the next week", just as we do in "in the last year" case?

3. Does that rule include other time phrases as well?

Next year, we are going to Italy.

but

The project won't have been done by 2016, but the next year will be ours.

4. "I have a job interview ON Monday", but "I have a job interview NEXT Monday". Why do we drop "on" there?

1. Yes you can use present perfect for those periods. Depending on context, you might prefer the simple past.

2. Right. Next week is called next week, not "the next week".

3. Yes it applies to years as well. Your Italy example is correct.

4. Actually, you could keep the "on" if you like, but it's not needed. But it's not needed in the first case either—you could drop the "on" and say "I have a job interview Monday." It may be more common to hear "on Monday" and "next Monday", but that does not make the alternative constructions "wrong"