In regards to your questions, Schradinger, yes, it is impossible to create something from what is basically nothing. Same basic laws of physics still apply in the realm (conservation in this case). That said, from the get go, I can see two possible ways for a loaf of bread to be 'conjured'. The first is in basic transmutation (equivalent exchange), as it is possible, although transmutation isn't the easiest effect to cast a spell for, as there are many variables involved in the shifting of matter's properties. Thus, although entirely possible, it isn't something to rely solely on, especially in regards to resources needed for basic living. The second way would be in conjuration, in terms of shifting the location of matter, that is: teleportation. Now, teleportation is also very difficult to do because of a different set of confounding factors that make the spell harder to execute but for the intent of summoning a loaf of bread, it is possible.

Your second assumption is also correct in that everyone has the [i]potential[/i], but potential is far from the actual ability. See my answer/discussion on the question: "Does magic come from within the individual or from the natural magically saturated environment?" which details this thing a bit more.

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Yes, you are right in thinking that one could use a different set of steps to achieve the same affect. It's one of the most unique (and enjoyable, in my opinion) parts of this magic system. Still, for the sake of the OOC, a rule of thumb is that more 'powerful' spells should have more difficult and longer preparations/executions, just to stave off any [s]metagaming[/s] godmodding and the like.

I recall alluding to this when speaking about a child's magical outburst.

This "different method, same product" factor only exists on certain spells though, particularly the very common and basic ones; Other spells have yet to be replicated by other steps (that doesn't mean that they can't be though), and in fact, figuring out the steps for any spells is a long process, involving a lot of experimentation, trial-and-error, practice and reasoning. This is why witches (especially those within the same coven) stick to the same way of casting a spell, for finding another way wouldn't be very pragmatic.