What function is performed by sigma factor and rho factor in the process of transcription?

Which of the following statements are correct?
$(i)$ From one molecule of $\text{DNA}$,several molecules of $\text{RNA}$ can be formed.
$(ii)$ The $\text{RNA}$ forming part is known as the translational unit.
$(iii)$ The promoter is located at the $5'$ upstream end.
$(iv)$ The promoter and terminator flank the structural gene in a transcription unit.

The process of removing introns and joining exons in a defined order from $RNA$ is known as.........

During transcription,the holoenzyme $RNA$ polymerase binds to the $DNA$ strand,and the $DNA$ forms a saddle-like structure at that site. What is this sequence called?

Splicing of $RNA$ means......

Explain different types of $RNA$ and explain the process of transcription.