How do the chromosomes appear in the given figure?

Select the correct statement regarding $S-$phase of interphase.
$I.$ Occurs between $G_1$ and $G_2$ phase.
$II.$ $DNA$ replication begins in the nucleus.
$III.$ Centrioles duplicate in the cytoplasm.
$IV.$ As $DNA$ is doubled,the number of chromosomes also doubles.

In which stage can chromosomes be counted?

The chromosome number in plants can be increased by

In mitosis,the spindle fibers are ........

In which phase of mitosis do the spindle fibers shorten,causing the centromere to split?