Support for a Beginner

Hi everyone.
My name is Jacob and I'm a pianist. I love to arrange and compose music, so I downloaded it last month and started with recopying scores that I already have to practice with them.
Since I'm new to arranging and composing, I have a few questions to ask:
1- I must download the latest version or update the one that I already have?
2- Can you give me links for tutorials of Version 4 to learn how to use all the features (especially new ones)?
3- How to download Muse Hub Application?
4- How to use plug-ins?
I am pretty sure there are some of the answers on the website but I don't know exactly where to find them.
Thanks in advance.