We explore the viable $f(R)$ gravity models in FLRW backgrounds with a free spatial curvature parameter $\Omega_{K}$. In our numerical calculation, we concentrate on exponential model of $f(R) = R - \lambda R_{ch}(1-\exp{(-R/R_{ch}}))$, where $R_{ch}$ is characteristic scale, which independent $\Omega_K$, and $\lambda$ corresponds to parameter, while $R_{ch}\lambda=2\Lambda$ $\Lambda$ cosmologi...