just would like to know if its possible to brew a beer over multiple weeks.I was thinking of brewing my next beer by adding a different hop every week for 3-4 weeks.And at each time adding more sugar and thus adding some more yeast to eat the new sugar added to produce a lil more alcohol each time.Is this possible??
Adding hops late in the process is pretty common, it's called dry hopping. It's a great way to enhance the aroma of hops, without increasing the bitterness too much. It creates a nice fresh characteristic in the beer.
Adding more yeast is not exactly common, but not unheard of. It can be used if the fermentation is stuck, and needs a kick. Sometimes yeast strains are intentionally mixed, but I think that's mostly done before they're pitched in the first place. Sometimes to create sour beers, or other styles, other fermentation strains are added after primary fermentation is done, like lactobacillous or brettanomyces.
Adding more sugar is also a common when bottling.
So there's nothing wrong with any of the steps you're thinking about. If you're interested you should totally experiment with it and see how it works out. I can think of two problems you'll have though. You're going to run a very high risk of contamination, you're opening up your fermenter and adding things to it multiple times. Also, eventually you're going to raise the alcohol enough so that it becomes inhospitable to the yeast. Keep an eye on your gravity and use appropriate yeast strains that can survive in the environment you're creating.
Dry hopping and secondary fermentation are not great things to do together.
Dry hopping is best done after fermentation, preferably after racking the beer off of the yeast cake. The acids from the hops will actually stick to the yeast (that's how they inhibit the growth of bacteria, etc) reducing the flavor.
I also suspect that having active fermentation will scrub some of the aromatics out of the beer. At the same time, since the hops carry some air into the beer, live yeast are needed to clear up the oxidation. But you don't want a lot of yeast activity.
In terms of adding fermentables, I think the most likely result will be a sweet beer and/or slow fermentation. It is common to do this for a barleywine, but that style is allowed to ferment for many months (and residual sugar is desired). Lambics also combine old and new beer (and multiple yeast strains), but again, they are allowed to ferment for a long time. These styles are great, if you're willing to wait for them.
It seems that you are just looking to increase your final alcohol percentage. If that is the case, consider bottling up some of your beer in plastic 2-litre bottles and throwing them in your freezer for a day or two. The water content of the beer will freeze, but the flavor compounds and alcohol won't. Once you've got an ice-cube floating in the middle of the bottle, pour off the still liquid contents into a sterile bucket and then bottle it. You will loose some volume, but the resulting beer will be substantially more flavorful and alcoholically strong.
This technique is called Freeze Concentrating or Freeze Distilling.
Check with your local authorities to make sure that it is legal where you live.