This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
You can take the Part II and III any time after you are qualified in Part I. But, I suggest you to take Part II immediately. If you take any gap then you tend forget the UML and patterns. And as you know Part III is about the assignment (partII). Hence it is always good to finish Part II & III soon after you are done with Part I. Part II and Part II are fun.