Android Execute Multiple AsyncTask Parallely

Hello All I am a bit confuse about execute multiple asynctask parallely in Android

Before Donut it was just single processing means we can execute only one task at a time but later it has changed and we can execute multiple async task parallely, in that case there was also limit to execute the multiple async task that we can execute only 138 Async Task thread at a time other wise it will through exception but later of honeycomb it has changed and we can execute 5 async task at a time and 10 can be in waiting queue, but if we execute more than 15 async task at a time means if I will execute 16 task at a time then it will execute 6 task parallely and 10 will be in queue, it means there will be atleast 10 task in waiting queue to wait for working thread to get finish, and also later in Kitkat it has been changes and it first get the number of processor running currently in Vm and according that it will execute the multiple asynctask.

Now My Questions are that: 1. what is the problem to execute multiple async task parallely. 2. why is the limit to execute only 138 asynctask at a time. 3. why does it differ with the android version. 4. what does it exactly means in kitkat to get number of processor currently running in VM and according that it will execute the asynstask. 5. what does asynstask use in background to track the waiting asynctask and Running Task.

Please Response For My Questions.