If $$\frac{\sin^{2} \theta-3\sin \theta +2}{\cos^{2} \theta}=1$$, where $$0^{\circ} < \theta < 90^{\circ}$$, then what is the value of $$\left(\cos2 \theta-\sin3 \theta+\cosec2 \theta\right)$$

A

$$\frac{3-4\sqrt{3}}{6}$$

B

$$\frac{-3-4\sqrt{3}}{6}$$

C

$$\frac{-3+4\sqrt{3}}{6}$$

D

$$\frac{3+4\sqrt{3}}{6}$$