start app on startup and click coordinate I want the tethering app to start whenever I start my phone, when the tethering app starts there is a big button on the center of the screen which has to be pressed so the phone would start to tether. 

I can achieve the above steps using ADB commands, but is there a way to create a script and place it on the phone so when ever the phone it boots the script also runs? if so, how? My phone is rooted.
Use an automation app, most of them has built-in support for starting various types of tethering, so it may not be necessary to automate the actual button press. But if that's the only option, it can probably also be automated with any of the following apps:


Automate
(free)
Automagic (paid)
Tasker
(paid) +
AutoInput
(7-day trial)