No, the police don't have to tell you that you can have a parent present. Yes, you can get in trouble for lying to the police, but it is very unlikely that they will prosecute you. This does give you grounds for a 5th Amendment claim if you do not want to testify against your boyfriend. You would be advised not to testify, because if you do, you will either have to lie on the stand, which is perjury, or you will have to admit that you lied to the police, which would subject you to prosecution. If that is the case, when you get subpoenaed, you can contact an attorney or the public defender if you can't afford a private attorney, and discuss your rights as a subpoenaed witness. Good luck to you.
Yes, you can get in trouble for lying to law enforcement. I hope that, in accord with up-dated practice, your interview was video/audio taped. If not, you might have a tough time convincing the DA, or more importantly the jury that you were lying. Talk to the DA about dismissing based on your misinformation. Also, contact the defense attorney and the defense investigator and let them know as well. You should be aware that, by doing these things, you do open yourself up to being charged.
Although I am an experienced CA criminal defense and appeals attorney, I can not 'guarantee' that my answer is entirely accurate, since I have not reviewed all of the factual circumstances of the case, nor have I discussed those circumstances fully with the questioner. The fact that I have answered this question does not establish an attorney client relationship between the questioner and my self or my office.
The police can question you without your parents present. They should but do not have to have your parents present.
You could get in trouble for lying to the police but it is very unlikely. Since you are a minor and were being questioned without your parents, the fact that you exaggerated is not unusual. No prosecutor is going to file charges against you. It is very unlikely you will get in trouble.
Your boyfriend's attorney should have an investigator interview you. That interview report should be provided to the DA in an attempt to get some or all of the charges dismissed.