Let \( f \) be a continuous function satisfying \(\displaystyle \int_{0}^{t^{2}} \left( f(x)+x^{2} \right) \, dx = \frac{4}{3} t^{3}, \, \forall \, t>0 \). Then \(\displaystyle f\!\left( \frac{\pi^{2}}{4} \right) \) is equal to:
\( \pi \left( 1 - \dfrac{\pi^{3}}{16} \right) \)
\( -\pi^{2} \left( 1 + \dfrac{\pi^{2}}{16} \right) \)
\( -\pi \left( 1 + \dfrac{\pi^{3}}{16} \right) \)
\( \pi^{2} \left( 1 - \dfrac{\pi^{3}}{16} \right) \)