The first boss is similar to the 002-C boss, but easier. Make a 50-man fist and hit him a couple times, then Guts Block all three of the smash attacks he's gonna do. They have various speeds, for watch out for that, but if you press Guts as soon as he starts moving down, you'll get it. As soon as that's done, get your 50-man fist out and start wailing on him again, as he usually moves to the "Grab hold of the arena and flip it over" attack, but as long as you keep hitting him, it'll disrupt the attack. Sometimes, he'll fall down a lava fall. When the camera comes back, make your 50-man fist, because he's gonna slowly rise up all pissed and that's a perfect time for a free combo. You do like I say, he should be dead right there, the fist does a LOT of damage.
Then there's the Punch-out!! tutorial, which is pretty straightforward. You can guard all the Evade UFOs, which kills them and gives you 300 points each.
For the Punch-Out!! boss, dodge away from every eye/eyebrow and combo him afterwards. Jump the kicks, dodge the rocks/lasers/uppercuts. Once you learn his moves, he's not so bad. You don't even have to do the whole "Look for secret ways to earn KO stars" thing as long as you attack him after every attack. Eventually you'll stun him with blue stars, which means its the perfect time to hit him with that SUPER-TRI-LASER you've built up. After that, he'll have a yellow bar, and he'll do the same thing. Eventually he'll jump back and do that Super Macho Man/Mr. Sandman thing where he'll telegraph his next few moves. If it's less than five, you can just block them, otherwise you gotta dodge.
When you go inside, quickly whip out a big Bomb, then send your 80+ people Attack Liner into him a couple times and he's dead. Bomb + Attack Liner is hilariously broken for several of the supposed tougher encounters in this game, and this will save you a lot of time and any potential damage.
Finally, the Volcano escape. Stay in the upper left or right hand corners. When he does the fireballs, move down and over the other corner to avoid them. When he does the drill, just stay where you are for a second, then dodge out of the way when he's about to reel back. When he does the laser, stay on the right/left middle of the screen, as it's either gonna be vertical or horizontal and you can avoid them.
Do all that without getting hit, boom, Platinum trophy.