If ${\tan }^{2}x={\cos }^{2}x-{\sin }^{2}x$  then which is/are correct

Number of solutions in $[0,n\pi ]$  is 12 then the value of n = 6

The value of  $\left[{\tan }^{4}x\right]=1$ ([.] is G.I.F)

Number of solutions in $[0,n\pi ]$  is 10 then the value of n = 5

The value of  ${\tan }^{2}x=\sqrt{2}-1$