I have lot of build's definitions using tasks (TFS 2015 vNext), Some of them need to run from middle of running process how can i perform that case
Thanks
Seems what your described is very likely chain the build definition. This Feature is under plan, but don't have yet.
Check the QA on this website:
Can I chain builds so that one build triggers another?
Not yet.
There's also an ancient suggestion on User Voice under planned , you could track the status.
Also take a look at this similar question: How to chain builds in TFS 2015?