Treating a sample with water, how to deduce present compounds given precipitate and solution parameters?
You correctly point out that Cl "is soluble with all the given metals". This statement is a little unclear, though, which might be why you're confused. What this means, exactly, is that no precipitate that incorporates Cl can form. For example, the solid $\ce{KCl}$ cannot precipitate, because the combination of $\ce{K}$ and $\ce{Cl}$ is soluble.

This fact alone doesn't forbid precipitates of other species. For example, the solid $\ce{BaSO4}$ is insoluble in water. We know that $\ce{BaCl2}$ alone would be soluble in water, but the barium atoms in $\ce{BaSO4}$ don't care that there are $\ce{Cl-}$ ions in the solution; all that matters is that the combination of $\ce{Ba}$ and $\ce{SO4}$ prevents the two from separating. As a consequence, when $\ce{Ba^2+}$ and $\ce{SO4^2-}$ meet in solution, they merrily form the insoluble product $\ce{BaSO4}$, regardless of the other ions present in the solution.