They can actually elute in either order. It depends on your mobile phase. In a weakly basic solution, the phosphate ions are found more as HPO4 (2-) rather than PO4 (3-) and thus will elute before sulfate which is larger and has the same charge.

In a strongly basic mobile phase, the PO4 (3-) ion will dominate, and will elute after the sulfate ion

Usually, but not always. Depends on the bond position and polarity of the column. Alkenes are less likely to elute first on polar columns.

chloroform

The Time-Taken the sample Or elute in the column is called the retention time in hplc.

Elute, Ettle, Tutee, Lute, Teel, Telt, Tutu, Eel, Ut, Te, Et