The nourishing cells in the seminiferous tubules are

Given below are two statements:
$Statement-I$: At the onset of puberty, the pituitary gland begins secretion of gonadotropin releasing hormone.
$Statement-II$: $GnRH$ initiates the significant increase in the secretion of follicle stimulating hormone $(FSH)$ which induces gametogenesis.
In light of above statements, choose the correct appropriate answer from the options given below.

Sertoli cells are found in the testis. What are these cells called?

Which part of the given diagram contains enzymes necessary for fertilization?

Which of the following phases in the development of a sperm has no counterpart in the development of an ovum?

Do all the gametes formed from a parent organism have the same genetic composition (identical $DNA$ copies of the parental genome)? Analyse the situation with the background of gametogenesis and provide a suitable explanation.