My analysis of the 3DS e3 trailer
Fighter Scales: seems to work very similar to the difficulty system in KI:U. 2.0 is the default. You can pay 300 coins for 0 difficulty. for increasing difficulty, may be 100 coins = 1.0 increase
Classic Mode: So it's paths that you seem to choose your opponent before getting to the fork. Each path has rewards of varying worths (ie coins, a Gogoat trophy, etc.). The silver coin is likely worth a different value than the gold. Star Fox path had a large circle likely indicating a special event( like Target Blast and the like). Before facing foes, we now see the stage as well as the character were fighting so that's nice. There is a rewards spinner on the bottom screen, likely to have better rewards on higher difficulties. I'm not sure what each icon means and it was spinning too fast for me to catch what most looked like but there were red and yellow in addition the green thing that was times 2. Thinking this green icon might indicate trophies as a reward.
Next is the victory screen. We know how this works.
Home run contest: As far as I can see, still works the same as Brawl. The Sandbag was hit at 132% and went over 1700 ft.
Online smash: Not really much new, though I think these icons are different from the ones shown for Wii U. After selecting For Fun/Glory, you choose between regular and team. Don't think anyone really notices or cares but having two players leaves a lot of black space that's kind of ugly. Also, noticed that the 3DS used in the trailer changed from Ferui8 to Quarl 10z. Also demonstration of that targeting touch screen function
Outlines: Pretty self explanatory and simple choose between thick, thin or none.
Smash Run: We also know this now. Yoshi back airing into a monoeye, hammer bro and I think a LoZ enemy. There was also this flying flower enemy. Next Link spin attacking Kihunters and a Kid Icarus enemy. The Smash Run ending battles: Flower Smash, Race. The powers is pretty detailed it seems. Y allows you to favorite certain powers, putting a star in the first column next to the power's icon. X is random, likely giving you a random set of powers. The power's icons' background each indicate its type. Red is a direct attack, gray are items, Orange is a buff and I'm not sure about Yellow but guessing Indirect Attack. Each power has a level, though I'm certain what it means. I'm guessing it's either it levels as you use them or it indicates the powers and number of times it can be used. Next column is seeing if its equipped. The final column is Weight as we can tell by the list being on Weight and it being the same for all those powers. Seeing how the equip icon highlights this column, it means that there is a maximum weight to determine how many powers you can use. The lower screen shows that the maximum is 24. I'm not sure what this "temporary"section is though. I believe we'll be able to sort the powers, alphabetical, by power type, weight, level, eqquipped and favorite at the very least. The bottom part of the top screen has a short blurb about the power, its type and uses. Uses are either how many times you used the power or how many are left. Top of the bottom screen is a bar indicating how much weight is used and how much weight will the power highlighted will add. Also noticed that this is another 3DS: Wirry_hud.
Rules: Mostly the same as Brawl, new option with turning customized movesets off and on. Also, stage switch is a unlockable again.
Multi Man Melee: Fighting Miis on Battlefield.
Pictures: Seems like you can arrange pictures into albums
Music and Voice test are returning
Target Blast: We know what it is but, with the score indicator, we can definitely say that you can use more that one bomb to blow up the targets. Also, the stage for this is unique rather than looking similar to the home run contest, looking more like a Colosseum than a stadium.
Next screen is likely showing if you customized a character's moveset
Team Pie Graph. Not sure what this is, maybe a tournament system or betting
Tips: short details explaining items, attacks, certain mechanics(ie stepping stone jump)
Crate breaking minigame, seems to have trophies, coins as rewards. Combo is likely held by the Fever bar as crates fall off the side but the score isn't reset. Likely lasts 3 minutes
Fighting Records. Character usage and stuff
Betting: spectating on an online match, looks like you have to watch the whole match to win the gold but leaving will return the gold you bet. Winning streaks seem to increase your bet
Trophy Diorama- The floor pattern is the smash symbol with the grass being the cross. Likely, all the trophies fill up the entire space
Icon minigame. Seems like a multiplayer minigame where to control via screen by launching your fighter into your opponents to knock them off. Defeating opponents earn you coins
Master hand, Kirby just beat him