I'll deal with your second question first.
When a moot talks about jury instructions, it is asking you whether the law, as stated by the judge is correct or incorrect. You can't appeal the jury's decision, as it is an issue of fact (except when a case is referred by the CCRC). Instead, appeals are made against the judge's instructions, arguing that since his instructions were wrong, the verdict is necessarily void.
For example:
Mr Sillyface is charged with assault occasioning ABH. At the conclusion of the trial, Judge Dimwit tells the jury that if they are satisfied beyond reasonable doubt that Mr Sillyface caused pain, then they should return a guilty verdict.
Mr Sillyface's lawyer, Ms Smartypants, lodges an appeal against the verdict, arguing that Judge Dimwit's instructions were wrong at law. He stated that the test was whether Mr Sillyface had caused pain, but the proper test that he should have put to the jury was whether or not there was visible physical harm (for example).
Regarding your first question:
Read the statute. Work out what the requisite mens rea is, and then go to the cases to find out how it has been interpreted and applied. Smith and Hogan on Crime by Ormerod is an excellent resource for doing your research for criminal mooting, and I would suggest having a look at it.
Hope that helps, and good luck.