Configure Rasberry Pi

Our company is prototyping the use of the Rasberry Pi (Raspberry Pi 3 B+) for a business use. (We are a B2B Music streaming business that creates bespoke custom playlists and scheduled for hospitality and retail businesses) The Pi we are using comes with a case has a 'reset button' integrated into the case. The Pi's will be used with displays or input devices I am seeking help (code and instructions on how to install & configure) to enable the Pi to do the following: 1/ On start-up, open a browser (or other direct OS based method) to have the Pi point to an audio stream (eg: [login to view URL]) - and play the stream without any problems. Will need instructions on how to change this for each new Pi we configure. 2/ If the stream has problems we need our clients to be able to safely reset (reboot the Pi) OR shut down the Pi. To this end we require the code written that can utilise the hard button on the pi case to: a) reset if the button is held for more than two seconds but fewer than five seconds; and to b) shut down if the button is held for more than five seconds. maybe using something like this: [login to view URL] 3/ ssh into the machine to do anything on it as required ) (eg: set wifi password if required, etc) As important as having the code written we need SIMPLE & SPECIFIC instructions that non technically minded people can follow to configure the Pi's GPIO, software files, etc to have this working every time we need to configure a new Pi for each new client