What are the packages which need to be installed for writing scripts using PyJius in system ?
Is there anyway by which i could run these python scripts on android phone ? 
What is K ivy Launcher for android ? Will it be helpful for executing my scripts ?
How actually Kivy works ( in detail say in I want to switch on Bluetooth using scripts, which are the things in the K ivy architecture gets invoked by doing so ? )
What i need is to write scripts on computer and then  after sending those scripts to my phone, then i need to execute my scripts from phone. Get the results on the phone and send those results to system.
What are the packages which need to be installed for writing scripts using PyJius in system ?

I'm not sure what you mean here. To run use pyjnius, all you need is...pyjnius. It is a separate module, not part of kivy itself, though kivy uses it on android. Kivy's mobile build tools automatically package this when you build an android apk.

What is K ivy Launcher for android ? Will it be helpful for executing my scripts ?

An app that can dynamically open kivy apps from your user data directory. You can use it to upload and run kivy scripts/apps on your device.
It is most useful for quick tests, not as a way to distribute apps. For this, it's very easy to build your own apks, which gives a lot more flexibility in what you do and what you package.

How actually Kivy works ( in detail say in I want to switch on Bluetooth using scripts, which are the things in the K ivy architecture gets invoked by doing so ? )

I'm not sure what you're asking here. Kivy is a graphical framework for python, using an optimised opengl interface...you write python gui applications with it.
For things like bluetooth on android, you can use pyjnius (or more easily, wrapper projects like plyer providing an abstracted python api, though I don't think plyer has bluetooth quite yet). This generally isn't very hard, I've seen bluetooth done before.
Kivy itself is a graphical framework, these other tools are sister projects but separate from the graphics.

What i need is to write scripts on computer and then after sending those scripts to my phone, then i need to execute my scripts from phone. Get the results on the phone and send those results to system.

You can certainly do this with kivy, by putting the scripts in an app that you run. Network communication also isn't hard - it's separate to kivy itself, but you have access to all the normal python modules you might use.
Kivy for android