Penal Code section 261(a)(4)(C) basically says that inducing someone to have sex through fraudulent means is rape.
And yes, the individual would likely get sued.
Posting the video on the internet would a) make it more likely the person would get sued. There are also a few other crimes that might have been committed.
If you or someone you know engaged in this conduct you/they really need to hire a laywer.
How many times they would have to appear in court is anyone's guess. Court cases can drag on for months and sometimes years. Without knowing all of the facts it is impossible for anyone to give you a realistic estimate of possible sentences.
As a general rule they can dismiss and re-file once. There are some very, very rare exceptions to this which seldom come into play. If you are out on bail be sure and stipulate to the re-file or the court may refuse to transfer your bond over.
Probably not. You already plead and paid the fine. You should consider hiring a lawyer in the future to try and take this off of your record. I'm not familiar with that code section, it looks like a local ordinance. Talk to an LA attorney and its likely you can clean up your record if you don't have any other run-ins with the law [and assuming you don't have a prior record].
Don't do it. Kissing is probably not illegal unless some DA decides they want to charge it as 'grooming' behavior. Also be careful about more general allegations of contributing to the deliquency of a minor - the deliquency statute is very broad and covers a lot of different conduct. Without knowing more about the specifics of your relationship it's hard to give you a better answer. Be careful about what you write on text messages/emails - under certain circumstances 'sexting' can be...
A person does not have to be in handcuffs in order to be 'under arrest'. Whether or not a person is 'under arrest' is a factual analysis and takes into consideration what law enforcement had told the person, whether or not a reasaonable person would feel free to leave, and other factors. Determining if a person is legally 'under arrest' for search purposes is pretty complicated - if you have more questions you should retain a lawyer and explain the facts specifically to that lawyer. And...
This is a very hard question to answer without a lot more information. Whether or not you should appeal depends on whehter or not there were any legal errors in your trial. The best thing for you to do is to file the notice of appeal [which you only have a limited amount of time to do] and then have an appellate lawyer evaluate the transcript. If the laywer says there is a basis for an appeal you should follow their advice.