Answer 1

https://www.sololearn.com/discuss/99903/?ref=app
https://www.sololearn.com/discuss/1479123/?ref=app
Check these out!

Answer 2

There are languages called general purpose programming languages that can be used in the 3 above areas, a few are
1.C/C++
2.Java
3.C#

When it comes to speciality however, certain languages stand outfrom their peers.

Games => C/C++
Enterprise level apps => Java
Systems programming => Rust/C++
AI => Python

SideNote::
I heard a new language called Golang can be used for network-heavy systems