Task dependency

Hi,

In a project I have 3 tasks say,

1. Drawing Preparation

2. Drawing Approval

3. Purchasing

Task 2 is dependent on task 1 and can not be started until and unless task 1 is completed. Similarly task 3 is dependent on task 2 and can not be started until and unless task 2 is completed. This is what my requirement is.

Now I want to know in Project Management if I try to update task 2 or 3 directly instead of task 1 then will system allow me to do so? or it will restrict from doing so? What is the standard functionality of Oracle R 12.1.3 ?

Regards

Chaitanya Adnaik