In which phase does the synthesis of spindle fiber proteins occur?

Which phase of interphase is the most important point in regulation of the cell cycle,during which it must decide whether the cell will start a new cycle or will enter in $G_0$ phase?

The phase that occurs before $DNA$ synthesis is known as:

Identify the correct stage of mitosis by viewing the diagram carefully.

$A$: The duration of the cell cycle varies in different organisms.
$R$: The duration of the cell cycle varies in different types of cells.

Which of the following phases is non-divisional?