Regarding the use of dilute sulphuric acid in this titration
A little bit of sulphuric acid is used when preparing iron(II) solution. This acid prevents the possible hydrolysis of $\ce{Fe^{2+}}$ ion according to : $$\ce{Fe^{2+} + 2 H_2O &lt;=&gt; [Fe(OH)_2(s) + 2 H^+}$$ In case this reaction occurs, the added sulphuric acid will react and destroy the precipitate $\ce{Fe(OH)_2}$ according to the inverse reaction : $$\ce{Fe(OH)_2 + 2 H^+ -&gt; Fe^{2+} + H_2O}$$
Now, during the titration, the ion $\ce{H^+}$ is needed to carry out the reaction of permanganate on the ion $\ce{Fe^{2+}}$ . Hopefully you know this equation.
And concentrated sulphuric acid is not wanted, because it reacts strongly with water just during its dissolution. It produces a lot of heat.