Six friends - A, B, C, D, R, and S are sitting in a row facing North. Use the clues below to determine their exact positions:
1. R is to the immediate left of A.
2. C is second to the left of R and immediate right of S.
3. D and A are sitting at the extreme left end and right end respectively.

Question: Who is sitting to the third right of D, who is also to the immediate right of C?

Let's determine the step-by-step arrangement for the $6$ positions numbered $1$ to $6$ from left to right:
1. According to Clue 3, D sits at the extreme left end (Position 1) and A sits at the extreme right end (Position 6).

$$\text{Lineup: D, \_, \_, \_, \_, A}$$

2. According to Clue 1, R is to the immediate left of A. Since A is at Position 6, R must be at Position 5.

$$\text{Lineup: D, \_, \_, \_, R, A}$$

3. According to Clue 2, C is second to the left of R. Position of R is $5$, so $5-2=3$. C is at Position 3.

$$\text{Lineup: D, \_, C, \_, R, A}$$

4. Also from Clue 2, C is to the immediate right of S, which means S is to the immediate left of C (Position 2).

$$\text{Lineup: D, S, C, \_, R, A}$$

5. The only remaining empty spot is Position 4, which must be occupied by the remaining person, B.

$$\text{Final Lineup: D (1), S (2), C (3), B (4), R (5), A (6)}$$

Let's evaluate the question: "Who is sitting to the third right of D?"

* Position of $\text{D}=1$.
* Third right of $\text{D}=1+3=4$, which is occupied by B.
* Notice that Position 4 ($\text{B}$) is also to the immediate right of $\text{C}$ (Position 3), satisfying all conditions.