Front-end the part with which the user interacts.
usually people who write this are called layout designers what languages are used (Html, css, js)
Beck-end The northern part is the structure of the site due to which it works, this includes the DBMS, logic, etc. which languages will be used(python, php, java)
People who can do both are called: full stack developr
Highlight everything with your curser.
You have a raspberry pi connected to all the sensors and a code running to trigger if the sensors are triggered. Each sensor and keypad would run to a different input on the pi. They should al be able to be powered with a single cell lipo. Is that what you are asking?
I prefer to choose the technician A. It should read approximately 12.6V. Volts is the basic unit used to measure voltage and I think the technician B stating the mv units in her reading comes from the units of his multitesters setting.