请教各位,这样讲对吗1. a new play is on at the phoenix.2. when he star

请教各位,这样讲对吗
1. a new play is on at the phoenix.
2. when he started to complain about this wicked world by a knock at the door interrupted.
1. a new play is on at the phoenix. 这是个填空题,"ON"位置是空的我自己填的ON不只对不对,AT原来有的我也不太清楚.
2. when he started to complain about this wicked world, by a knock at the door interrupted在这里加逗号,对了吗?
非常感谢Sammishirh和marscuta!谢谢