Where to use read (),readline () and readkey ()???

Answer 1

read()
returns a integer value of the first character
do not use it anymore, readline is a beter option
https://msdn.microsoft.com/en-us/library/system.console.read(v=vs.110).aspx

readline
returns a string
https://www.dotnetperls.com/console-readline

readkey
returns a ConsoleKeyInfo.
This datatype gives a lot of information of the key(s) that was pressed.
It is easy to test which key it was
for example
if (info.Key == ConsoleKey.Escape)
https://www.dotnetperls.com/console-readkey

readkey does not work in the playground, so you have to test it in your own enviroment

https://code.sololearn.com/c9VAXYW9kMsD

Answer 2

I don't understand the question, isn't it obvious?