Task Completed Date

How to get a Task assigned date and Task Completed Date

Hi Community

I am trying to save the Details for each task. I need to collect 3 information for each task.
1) The date when the task was available to the group.
2) The Date when an approver has picked up the task
3) The Date when the Task was completed.

The available rest api shows the 1 and 3 Dates. not the 2 date.

Could Somebody suggest how I can proceed here.
Also is there any way to track if a user has accepted a task and then released it.
Could we use a groovy script to fetch these details and store in Database .