welcome to the site and congrats on the new to you honda
now as for a few of your things, a snow plow will work, but don't think anyone actually makes a EXACT fit plow blade mount for it, due to its age, your going to most likely need to buy a universal kit and mount it some how using the assorted drilled holes in the mount or having to drill some to work
I am a HUGE fan of the Moose mid mount plows, and for a 300 I think you will want a a 42 or a 50 inch blade, you need to really measure the width of the ATV< and get a blade that at FULL angle will still plow a path that the tires will NOT be in the snow
here is a link to the moose blades
Products ? Moose Utility Division
NOW< as for a Back blade, , I hate to bust your bubble, but you are NOT going to use this atv to use one, it just will do NOTHING but make atv spin its wheels
a ATV simply does NOT weight enough and have enough power if it DID to DRAG a back blade, your a million times better off BUYING a OLDER heavier tractor for this type of work, something with a rear PTO would be what you want, older and I mean OLDER 1950's-1970's tractors can be had pretty cheap if your any where near farm lands and or willing to GO get one, and I';m talking $1500 bucks like cheap they will weight 3-4-5,000 lbs and will WORK,
OUT WORK a atv by a HUGE margin and be simple things to up keep, them older tractors were designed for un educated farmers to work on them! and I am NOT insulting farmers here, its just how they were designed, so average folks can up keep them
NOT like newer things which almost ALWAYS need to have a high skilled tech service them
a SECOND reason to get a smaller older tractor is, you can get a brush hog to pull behind it, and your ONLY running one motor, where if you drag a mower behind an ATV< your running two motors twice the fuel and wear and tear
PLUS a used brush hog will be CHEAPER to buy and WAY more heavy duty than what they sel and make for a ATV, due to again WEIGHT of what a ATV can handle
you need to remember this small honda 300 is NOT a very heavy atv, it might be geared low and have good power, but it will be easy to have NOT enough traction to pull heavy things and or push Deep WET heavy snow
SO< my advice is, get a snow plow of correct size to this atv, you can get into places on an atv you cannot on a tractor, so its a win for plowing, as long as you do NOT wait for snow to get too deep before plowing, as again deep snow in front of a atv plow blade and a VERY small atv here, you can have snow too deep to push on it
and then rather than buy a tow behind mower for it and a useless back blade for it, BUY a older used tractor and get implements for it, they will be far less costly than ATV sized implements and well, it will get way more work done in half the time and save you lots of $$$ and time in the long run!
sorry if NOT what you hoped to hear, but honest as can be advice here for you!