word usage - Differences between "inform, tell, notify, and instruct"

When and how to use these verbs correctly? I believe that even though they sound synonymous, every word has its own proper usage in a sentence.

According to Merriam Webster,

inform- to impart or give information

tell- to make known; to express in words

notify- to give notice of or report the occurrence

Does it mean they are somewhat synonymous and can be used in a sentence interchangeably? For example,

1. I already informed/told/notified him about our plans this September.


2. Please inform/notify our classmates that we will have a long quiz on our History subject.


3. The police notified/told/informed the family that this is not just a mere case of suicide.