Which stage is indicated by the given figure?

In the anaphase stage,metacentric chromosomes appear as .......

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

During which phase of cell division do the chromatids move towards opposite poles?

Select the correct option on the basis of the following events:
$(I)$ Chromosomes cluster at opposite spindle poles.
$(II)$ Nuclear envelope assembles around the chromosome clusters.
$(III)$ Golgi complex and $ER$ reform.

What is the structure of the bipolar spindle composed of?