Arrin Canales , question 9 at 44:13 is another example of reactions of dienes, I recommend trying the question out first before seeing the answer. 

Shir Yes Nitrogen is an exception, whenever you see N having a positive formal charge and there's a nonmetal this is a type of ionic bonding. 

When there is an ionic bond we do not connect these atoms together, specifically the + bearing atom and - bearing atom, this is why the Cl is not bonded. At 12:54 Melissa shows the differences between Ionic and Covalent bonding and shows common examples to look out for. Overall when you see a metal and a nonmetal in the same structure they will not be bonded to each other instead we have to show the + and - charges. Does this make sense?

0 is typically better when possible, there are times when this is not possible because the overall net charge of the structure is not 0. But the more atoms that have a formal charge of 0 the better that structure is. 

We typically draw the line (substituent) going in the direction of the way that carbon is pointing. Think of carbon 2 as the letter V, the line is going in the direction of that point.

Does this make sense? 

There is no chiral center on the C that is connected to the OH. This has 2 of the same groups, it's the 2 CH2's on either side of the ring. This is why we don't show stereochemistry. There is only one product. 

Steric effects decrease acidity, if there is a bulky group as a substituent then this will make it less acidic. Bulky groups can interfere with the ability of the molecule being able to donate a proton (H+) which makes it difficult for this molecule to act as an acid. 

Solvation refers to the interaction of the solute (what is being dissolved) with the solvent (what is doing the dissolving). If a molecule is more solvated it means it's stabilized by the solvent and the opposite is true. 

Steric Effects and Solvation tend to go hand in hand. If a molecule is less hindered it is more solvated which makes it more acidic.