During cell division,the nuclear envelope reforms at which stage?

In which phase is cell division arrested for the study of chromosomes?

Decondensation of chromosomes occurs during

$A$: The complete disintegration of the nuclear envelope marks the start of metaphase.
$R$: Chromosomes are distinct with two chromatids at this stage.

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

In which phase of mitosis does the nucleolus disappear and the chromosomes become distinct?