Question

is potassium phosphate a binary compund

Answer 1

No. Wikipedia explains it well, so I will not credit myself for it:
A binary compound is a chemical compound that contains exactly two different elements.[1][2] Examples of binary ionic compounds include calcium chloride (CaCl2), sodium fluoride (NaF), and magnesium oxide (MgO), whilst examples of binary covalent compounds include water (H2O), carbon monoxide (CO), and sulfur hexafluoride (SF6).

Answer 2

Ignore the [1], [2].

Answer 3

A binary compd HAS EXACTLY 2 DIFF. ELEMENTS

potassium phosphate is K3(PO4) <-- this is 3 elements in one compound.