During lab, we tested HCl and its diluted solution which resulted as pH1.14 and diluted one was pH 2.05. Another dilution was also done using weak acid HC2H3O2 which had pH 2.86 and the diluted one being pH3.45.

Which acid pH changed the most on dilution: HCl or HC2H3O2, and it saids to explain why considering the equilibrium occurring.

In the case of HCl, as you said, it was 100% ionized, either way. What happens to the percent dissociation for a weak acid when it becomes more dilute? Try calculating the percent dissociation for acetic acid at 0.1 M and 0.01 M and compare the results.