From statement I alone -
Statement I: Two persons sit between S and W. V sits immediate left of P. Four persons sit between X and T, who sits second to the left of R. Only one person sits between P and Q. R sits fourth to the right of S.
Four persons sit between X and T, who sits second to the left of R.
R sits fourth to the right of S.

Two persons sit between S and W.

V sits immediate left of P.

Only one person sits between P and Q.

So, statement I alone is not sufficient.
From statement II alone -
Statement II: R sits immediate right of W. Three persons sit between Q and S, who sits in the middle of the row. P sits third to the left of T. Q sits second to the right of V. The number of persons sitting to the left of V is same as the number of persons sitting to the right of T. V does not sit adjacent to U.
Three persons sit between Q and S, who sits in the middle of the row.
Q sits second to the right of V.

The number of persons sitting to the left of V is same as the number of persons sitting to the right of T.
P sits third to the left of T.

R sits immediate right of W.

V does not sit adjacent to U.

Q and R are sitting at the end of the row.
Hence, the data in statement II alone are sufficient to answer the question, while the data in statement I alone is not sufficient to answer the question.