What is the recipe? How long has it been? Do you have a hydrometer?
Usually speaking if you are relatively good at sanitation, it seems to be pretty forgiving. Any off odor will most likely go away with time and aging.
Again, with tasting, as long as you are sanitary, you should be fine. How did you collect your sample? How much did you take? What size batch is this?
Yes the flavor will change the more you let it sit. As it ages, any alcohol hotness will mellow out, and all the flavors should blend together smoothly.
The sediment (I am assuming you have not racked into another carboy or bucket yet) is just the yeast and their by-products. DO NOT STIR Before you bottle it would be best to rack (siphon) off of this sediment so as to not mix it into your bottles. But more importantly, you should to wait until the cider is perfectly clear. Most people say you should be able to read a newspaper through it.
And if it isn't bubbling, that just means that at least the bulk of the fermentation is complete.