We call them wat inspired Sakurai to make Crazy and Master Hand, plus Mario in his 8-bit form.
No and yes.
Master Hand was born out of the idea that Smash Bros. was a child playing with his toys, although his laugh makes him sound like a middle-aged man living in his parent's basement. There was speculation it was Mario's glove, but that had so many holes in it. For one, the voice is completely off. Another's that the hand's attacks are nothing like Mario's, he flies around and shoots rockets. The crowning piece of evidence is the opening, where the hand actually picks up the characters and places them on a battlefield. He's also the cursor of the select screen in 'Melee, not being too blatant though. The child is not shown, so you could also say that although Master Hand represents a child's imagination, he's a completely different entity altogether. I wouldn't bet against him being a demonic creature that forces the characters of Smash Bros. to fight until Ragnarök.
Crazy Hand is supposed to represent or be the destructive side of the child, he's essentially a clone of Master Hand. They're also representative of left and right hands, giving more ground to the claim they are the "hands of a child", even if they sound like evil slobs. Crazy Hand's attacks are akin to a psychopath, with static movements, rapid attacks and arguably harder to avoid moveset. Even though they're both opposites, they do perform a few double-team attacks. Meaning they have a relationship with each other of some sort. Or you could ignore all I've said, and realise they are just bosses. They may have nothing to do with anything, or just be the friggin' cursor you use to select. But they have nothing to do with Andross! There is no connection! Andross' hands have jewels in the center of their palms, where you shoot laser beams to do damage! They would then be impossible for simple kicks and punches to destroy. And no, Andross has never laughed like Master/Crazy Hand.
Jumpman is the 8bit version of Mario. Except, you know, he's not a "version" but more of a downgrade. Mario has improved from that exact model to what he is now. He's still able to jump, which is the sole action Jumpman has available to him. If Jumpman could use any moves apart from an extraordinarily large jump, he'd either have to steal them from Mario ala the Doc or have something crazy like the moves of the enemies. It won't work. He'd also look bollucks. Who wants a sprite that fugly in 'Brawl? Nostalgia? Oh, please, we'll have Sonic, Balloon Fighter, Megaman and maybe even the (unlikely) returners ICs and G&W. We don't need another Mario.