Explanation:

Alright, let’s break this down:

- O is at the left end, so the first house is O.

- S is third from the left, so S is in position 3.

- M is second from the right, that's position 6.

- P can't be at the ends, so can't be at position 1 or 7.

- R is immediately to the right of P, so R is right after P.

- P can't be at position 7, 6, or 1 (because of R and end rules), which means P can only be at position 4 or 5.

- O is not beside N, so N can't be position 2.

Now, let’s fill:

1. O

2. __

3. S

4. P/R

5. R/P

6. M

7. __

Try P at 4, R at 5:

1. O

2. __

3. S

4. P

5. R

6. M

7. __

Now, Q and N are left for positions 2 and 7. O is not besides N, so N can't be at 2 (since O is at 1), so N must be at 7. Q takes position 2.

Final order:

O Q S P R M N

Let’s check the position of R: O(1), Q(2), S(3), P(4), R(5), M(6), N(7).

From the right, position 7 is N (first from right), M (second from right), R (third from right).

So, R is third from the right.

Option 4: Third from the right