I'm new to recording. I mean one week new. Ok, here are my questions:
1. Where do you upload your playing (my space? Soundclick? Your own site?)
I usually use my own site.
2. If I record myself playing a popular song (me playing all the instruments and singing) and it's not for profit, am I violating the copyright?
Yes. Profit or not, US Copyright law considers distribution the infringing act.
Releasing your own cover recordings of music composed by another artist requires what's called "compulsory license". It's compulsory in the sense that an artist is required to grant you license. You can be denied permission to use their recording, but you cannot be denied permission to re-record previously published material. However, there are specific rates based on union and ASCAP/BMI guidelines, that must be paid for use of the material. It is advised that you or a competent IP attorney contact the copyright holder for permission first. Otherwise, you're inviting a lawsuit.
The fines for violating copyrights are pretty substantial... in the five to six figures. And that's just the statutory fines. That doesn't include civil damages which can be awarded on top of criminal penalties.
Bands that play cover songs in public venues are covered because public venues that broadcast music (either live or recorded) usually have a licensing agreement with one or more performing rights societies (e.g. ASCAP, BMI, SESAC, SOCAN, etc.) who control the distribution of royalties to their members. But a sound recording is not covered by a blanket license from ASCAP, BMI, etc. There you need compulsory license to be granted... or, in the case of reproduction of the original recording, mechanical license for which the copyright holder can charge whatever they want.
Note that if you put it up in a place where it can be downloaded, it is considered distribution. It doesn't matter how many people actually downloaded it. If you want to share it with your guitar instructor, then go hand them a physical copy of the recording. The problem is that the internet, and public access to it, risks undermining any "fair use" counterargument that educational instruction falls under. Direct conveyance between student and teacher would suggest fair use.