  Using the full data sample collected with the Belle detector at the KEKB
asymmetric-energy $e^+e^-$ collider, we present three recent measurements of
time-dependent CP violation in $B$ decays, and a measurement of branching
fraction of the $B^0\to\rho^0\rho^0$ decay. We studied $B\to\omega K$ decays
and measured the values of CP violation parameters in $B^0\to\omega K^0_S$ to
be $A_{\omega K^0_S} =-0.36\pm 0.19(stat)\pm 0.05(syst)$ and $S_{\omega K^0_S}=
+0.91\pm 0.32 \pm 0.05 $, which gives the first evidence of CP violation in
this decay. In addition, we measured the direct CP violation in $B^+\to\omega
K^+$ to be $A_{CP} (B^+ \to \omega K^+)=-0.03\pm 0.04 \pm 0.01$, and two
branching fractions $B(B^0 \to \omega K^0)=(4.5\pm 0.4\pm 0.3) \times 10^{-6}$
and $B(B^+ \to \omega K^+)=(6.8\pm 0.4 \pm 0.4) \times 10^{-6}$ (preliminary).
From the measurement of CP violation parameters in the $B^0\to\eta'K^0$ decay
we obtain $S_{\eta'K^0} = 0.68 \pm 0.07\pm 0.03$ and $A_{\eta'K^0} = +0.03 \pm
0.05\pm 0.04$ (preliminary), which are the world's most precise values to date.
Measuring CP violating parameters in the $B^0\to\pi^+\pi^-$ decay gives
$A_{\pi^+\pi^-} = +0.33\pm 0.06\pm 0.03$ and $S_{\pi^+\pi^-} = -0.64\pm 0.08\pm
0.03$. This result is used in an isospin analysis to constrain the $\phi_2$
angle of the unitarity triangle, with which we rule out the region $23.8^\circ
< \phi_2 < 66.8^\circ$ at the $1\sigma$ confidence level. The measured
branching fraction of the $B^0\to\rho^0\rho^0$ decay is $B(B^0\to\rho^0\rho^0)
= (1.02\pm 0.30\pm 0.15)\times 10^{-6}$, with the fraction of longitudinally
polarized $\rho^0$ mesons being $f_L = 0.21^{+0.18}_{-0.22}\pm 0.13$. We obtain
also the first evidence of the $B^0\to f_0\rho^0$ decay, by measuring $B(B^0\to
f_0 \rho^0)\times B(f_0\to \pi^+\pi^-) = (0.86\pm 0.27 \pm 0.14)\times
10^{-6}$.
