如图,\(AD/\!/BC\)且\(AD=2BC\),\(AD⊥CD\),\(EG/\!/AD\)且\(EG=AD\),\(CD/\!/FG\)且\(CD=2FG\),\(DG⊥\)平面\(ABCD\),\(DA=DC=DG=2\).
\((\)Ⅰ\()\)若\(M\)为\(CF\)的中点,\(N\)为\(EG\)的中点,求证:\(MN/\!/\)平面\(CDE\);
\((\)Ⅱ\()\)求二面角\(E-BC-F\)的正弦值;
\((\)Ⅲ\()\)若点\(P\)在线段\(DG\)上,且直线\(BP\)与平面\(ADGE\)所成的角为\(60^{\circ}\),求线段\(DP\)的长.