I did something I'm not proud of and wish I never did. My friend and I stole items between around $500 3 times at the Bay, getting caught the last . I told them everything as the people who brought us in were really good interrogators, and when I asked if I'd get a permanent record they said yes. A police came and gave us both tickets saying we had to get our fingerprints recorded and go to court. We were to never set foot in... (u no the rest), but they wanted me to return their merchandise the next time so I did.
I can't afford a lawyer. I'm 18 so I guess I don't have much chance? How should I protect myself when I go to court and what do I say to the judge? Most likely I'd have to plead guilty but I don't know how I can avoid a criminal record, for all I know they stay with you till you die. Tell me anything you know! Thank you!
In the end if I do get a record, does every employer have the right to check them?
Would I be able to go back to my home country china again?(I'm canadian btw)

I don't think there's any way of avoiding a criminal record, you would have to ask a lawyer about that, but in Canada, I don't know if they have the same deal as the US with a court-appointed lawyer being provided for you for free if you can't afford it.. If you get a record, in the end, which I'm guessing you will as $500+ is not considered petty theft and you are not a minor, then yes, every employer will be able to access that record.

Unfortunately I know nothing about chinese immigration laws and stuff... so I have no clue about that.

Welcome. Good luck with your trial and all, hopefully they go easy on you and you will learn your lesson to never do anything like that again.