New to Git / Questions about single user / multiple projects

I'm new to git and have some (I think) basic questions that I have not
been able to find answers to in the documentation.
It's very possible that these are the result of my lack in
understanding git / version control, so feel free to point me to
documentation
that might contain the answers.

I'm doing ERP development for my job and various 'hobby' development
in my spare time.
I'd like to track/store/ version control the code that I write for
both work and play.
I am (currently) working by myself, no need to have multiple
developers working of the same code.

Q1:
Can I create a single repository (project?) for all my code, knowing
that there are multiple small, unrelated projects. Or should I create
a new repository for each project ?

Q2:
After initalizing my repository, and comitting the 1st batch of code:
When further working on the code, will the command "git add ." add all
changed and new files ? Or do I specifically need to list the new
files ?

Q3: Can I run 'git add x' in any subdirectory, or do I need to issue
if from the root of the project ?

Thanks,

Rob.

--
When in trouble or in doubt, run in circles, scream and shout