Question

1.Some plays are so successful that they run for years on end, In many ways,

that是从句吗？
2.this is unfortunate for the poor actors who are required to go on repeating the same lines night after night.who是状从吗？
3. A famous actor in a highly successful play was once cast in the role of an aristocrat who had been imprisoned in the Bastille for twenty years.
in a highly successful 是定语吗 who是定从吗in the role of an aristocrat 是状吗
4、In the last act, a gaoler would always come on to the stage with a letter which he would hand to the prisoner.
to the stage 是宾吗with a letter 是状语吗 这句话是状从吗
5. One night, the gaoler decided to play a joke on his colleague to find out if, after so many performances,
play a joke on his colleague to find out if 解释下都是什么语，谢谢。

Answer 1

1.so...that 如此...以至于...that后面引导，结果状语从句
2. who不是引导状从，而是定语从句，用来修饰前面的the poor actors
3. a highly successful 是定语，修饰a famous actor；who引导定语从句，修饰an aristocrat；in the role of an aristocrat 不是状语，cast in 是个词组，这里理解为扮演 the role of an aristocrat，一个贵族的角色
4. 不是状语从句，是定语从句，which后面修饰a letter
5. play a joke on his colleague 是宾语
to find out if 是目的状语

Answer 2

这里不强调还在上演，所以不用完成进行时态；如果需要强调还在一直上演，就可以用完成进行时态。
这要根据上下文或者说话者的意思来进行选择。

Answer 3

是从句！