Can I Use an ECS Instance ID to Learn What AS Group the Instance Is In?

No.

To obtain details about an AS group and the instances in the group, perform the following operations:

1. Log in to the management console. Choose Compute > Auto Scaling > Instance Scaling.
2. On the AS Groups tab page, click the name of the target AS group.
3. Click the Instances tab to view the instances in the AS group.