What are the infoldings of the cell membrane in bacteria called?

In many bacterial cells,there is a small circular $DNA$ outside the genomic $DNA$. What is it called?

The true sequence for the cell envelope from outer to inner in prokaryotes is:

Which of the following statements about a bacterial cell is/are correct?
$(i)$ Mesosome is formed by the extensions of plasma membrane into the cell.
$(ii)$ The pili are elongated tubular structures made up of a protein.
$(iii)$ Flagellum is composed of filament,hook,and basal body.
$(iv)$ Ribosomes are about $30 \; nm$ by $50 \; nm$ in size.

Which of the following is not a structure of prokaryotic flagella?

In prokaryotes,the region formed by the cell wall and the plasma membrane is known as: