A lower bound for $L_2$ length of second fundamental form on minimal hypersurfaces

We prove a weak version of the Perdomo Conjecture, namely, there is a positive constant $\delta(n)>0$ depending only on $n$ such that on any closed embedded, non-totally geodesic, minimal hypersurface $M^n$ in $\mathbb{S}^{n+1}$,$$\int_{M}S \geq \delta(n){\rm Vol}(M^n),$$ where $S$ is the squared length of the second fundamental form of $M$. The Perdomo Conjecture asserts that $\delta(n)=n$ which is still open in general. As byproducts, we also obtain some integral inequalities and Simons-type pinching results on general (not only minimal) closed embedded hypersurfaces, and on closed immersed minimal hypersurfaces, with the first positive eigenvalue $\lambda_1(M)$ of the Laplacian involved.