A：$\beta$

B：$\sin \beta =\sqrt{1-{\cos }^2\beta }=\frac{\sqrt{5}}{5}$

C：$\tan \beta =\frac{\sin \beta }{\cos \beta }=\frac{1}{2}$

D：由$\left(2\overrightarrow{a}-3\overrightarrow{b}\right)·\left(2\overrightarrow{a}+\overrightarrow{b}\right)=61$得$4{\overrightarrow{a}}^2-4\overrightarrow{a}·\overrightarrow{b}-3{\overrightarrow{b}}^2$=61