Aniline behaves as a weak base. When $0.1 \mathrm{M}, 50 \mathrm{mL}$ solution sample of aniline was mixed with $0.2 \mathrm{M},$ $12.5 \mathrm{mL}$ solution of $\mathrm{HCl},$ the $\mathrm{pH}$ of the resulting solution was $8.$ Then:

Titration curves for $0.1 \mathrm{M}$ solutions of three weak acids $\mathrm{HA},{\mathrm{HA}}_2$ and ${\mathrm{HA}}_3$ with ionization constants ${\mathrm{K}}_1,{\mathrm{K}}_2$and ${\mathrm{K}}_3$ respectively are plotted as shown in the figure. Which of the following is/are true?

In above question, If $[\mathrm{X}{]}_{\mathrm{i}} : [\mathrm{Y}{]}_{\mathrm{i} }: [\mathrm{Z}{]}_{\mathrm{i}}=100:10:1 \& {\mathrm{K}}_{\mathrm{sp}}[\mathrm{MX}] : {\mathrm{K}}_{\mathrm{sp}}[\mathrm{MY}] : {\mathrm{K}}_{\mathrm{sp}}[\mathrm{MZ}]=10:0.1:1,$ order of precipitation will be:

Consider the coordination compound, [Co(NH₃)₆]Cl₃. In the formation of this complex, the species which acts as the Lewis acid is :