The detail answer is given in the explanation section.
Cyclins are among the most essential core cell cycle regulators. Cyclins are a group of related proteins. There are four basic types found in humans and most other eukaryotes. Each cyclin is correlated with a particular condition, transition, or set of stages in the cell cycle, and thus, they help to make the events of that phase or period.
A typical cyclin is present at the lower levels for most of the cycle but increases sharply at the stage where it's required.
i do not know and i have a 100 in this class