InCl₃ reacts with Cl^- and produces InCl₆^3-  because In is much more electronegative than B hence BCl₃ reacts with Cl^- and only produces BCl₄^-

BCl₃ reacts with Cl^- and only produces BCl₄^-, because B is a non-metal while In is a metal which is why it is able to form InCl₆^3-

BCl₃ reacts with Cl^- and only produces BCl₄^-, because B is not large enough to be able to hold more than 4 groups while In is large enough to form InCl₆^3-

InCl₃ reacts with Cl^- and produces InCl₆^3- and not InCl₄^- because In has 6 valence electrons while B only has 4 hence BCl₃ reacts with Cl^- and only produces BCl₄^-