Who divided the cell cycle into four phases (i.e., $G_1$, $S$, $G_2$, and $M$)?

Which of the following statements are correct for $G_{1}$-phase?
$I.$ It is the last substage of interphase
$II.$ Cell organelles do not increase in number
$III.$ Cell grows in size and content both
$IV.$ It synthesizes $RNAs$,proteins and other biochemicals for cell growth and subsequent replication of $DNA$
Choose the correct option

Cell division is initiated by

In which phase is the centrosome observed to be duplicated?

In humans, how many hours does it take to complete one full cell cycle (in $hours$)?

In which of the following cells is the cell cycle completed in $90$ minutes?