Let $G_1$ and $G_2$ be arbitrary context free languages and $R$ an arbitrary regular language. Consider the following problems:
- Is $L(G_1)=L(G_2)$?
- Is $L(G_2) \leq L(G_1)$?
- Is $L(G_1)=R$?
Which of the problems are undecidable?
Choose the correct answer from the options given below:
- $(i)$ only
- $(ii)$ only
- $(i)$ and $(ii)$ only
- $(i)$, $(ii)$ and $(iii)$