If you want to make everything rwx for everybody under /opt what you do is this:
chmod -R 777 /opt
Now anybody with an account can do anything under /opt, this is not recommended but you can start with this and then make it more secure when its working. For example, to just make it rwx for the owner of /opt you do this:
chmod -R 700 /opt
When it comes to choosing distro my opinion is that ubuntu is one of the more userfriendly ones and a great first distro, i wouldnt be here without it
But the next person will tell you some other distro is superior so you need to just choose one and stick with it.
Preferably choose one your friends are running so you can ask them when you get stuck
Good Luck!