Service chains packet processing for L3 devices

Hello, I'm trying to understand SSL intercept and Service Chains, and have a few questions about it:

According to a devCentral video, https://www.youtube.com/watch?v=mvse6zCt_jo , devices in a service chain are accessed in parallell, minimizing the delay in a long chain with many inspection devices. However, reading the SSL intercept deployment guide, it says " Each service chain is an ordered list of services of various types", that sounds like the devices are processed one at a time?

Question 2: When you hook up a L3 device in your service chain, does the complete packet get sent to the device and back again to the BIGIP (if allowed though the L3 device)?

Question 3: What about the return traffic, is it automatically send back to the sending interface of the L3 device? In my case the L3 device is a NGFW, I'm asking because I want to know if the traffic flow will be weird in any way from the NGFW point of view (statistics, logging and so on).