Questions about nutrition?

I'm new to rabbits and keep reading different things. Some have said feed alfalfa pellets/hay till 12 months others say 6 months. Some say no grass till 6 months others under 3 months. I heard that Oxbow is best, but also Sherwood Forest. Also to feed 1/4 cup per 6 lbs? How much greens/veggies should I be feeding a bunny/rabbit per day? Is it necessary to feed them greens/veggies or are they fine on just hay/pellets? Also, I have a large yard and don't have the money for fencing so should I use a harness? Lastly, how many lbs of feed per month do I need for a 10-12 lb rabbit? Thank you!

Alfalfa till 12 months if it's a large breed rabbit, 6 months if it's a small breed. If somewhere if between your bunny starts getting overweight, switch to timothy pellets/hay.

Your pellet brand of choice is up to you (and your bunnies' taste buds). Those two are good brands. Oxbow bags have feeding instructions on them.

Feed very tiny amounts of greens until after your bun is fully grown. Even then it should be no more than 5-10% of their overall diet. If they'll be eating grass in your yard, extra greens aren't necessary except as an occasional treat if you feel like being nice

A harness will be useful, rabbits can be very hard to catch if they want to be.

Someone else will be better at answering your last question, my buns are like 3lbs each.

http://www.bio.miami.edu/hare/diet.html
That should help with some stuff.
And this should help some more.
http://rabbit.org/faq-diet/

I feed Small World rabbit feed from Walmart. I don't have a problem with it at all, its got all the right percentages for what the rabbits need. I have a 2 lb dutch rabbit and she eats like a horse. Everyday she gets, 1/2 cup of pellets. 2 cups of greens; daily: cilantro, romaine lettuce; every other day: spinach, rosemary, parsley, basil. For fruits she gets, strawberry tops, blueberries, grapes, banana and apple; about 1 tbsp a day of fruit(probably WAY too much, but she does well with it and she loves it!) She gets unlimited timothy hay and fresh water from a bowl.

When she was a baby, I fed her a mix of alfalfa and timothy. I don't think you need to feed alfalfa when they're younger, I think just grass hay is okay as long as you're feeding an alfalfa based pellet. Which I was when my bun was a baby.
I've never used Oxbow because I think its insanely expensive and I don't want to pay for it. But I have used Sherwood, I didn't like it that much. They recommend that you feed unlimited pellets and they really mean it. My baby bun was eating almost 2 cups a day, yes 2 CUPS and she was still loosing weight and she had a dull coat. So I transitioned her onto the feed she has now and the rest of the Sherwood got fed to the chickens. Now feeding her the small world, she's shiny and she's maintaining a healthy weight.
I buy like 5 lbs a month of food and that lasts my one rabbit the whole month.

I don't think greens are necessary, but rabbits do really like herbs and lettuces. My rabbit loves grass too, so if you're taking your bun(s) outside, then they'll like grass too!
Hope that helps!