
Food is an artifact type. Even though it appears on some creatures, it's never a creature type.
You can't sacrifice a Food to pay multiple costs. For example, you can't sacrifice a Food token to activate its own ability and also to activate Maraleaf Rider's ability.
Whatever you do, don't eat the delicious cards.
If the copied creature has in its mana cost, X is considered to be 0.
If the copied creature is a token, the new token that's created copies the original characteristics of that token as stated by the effect that created that token, with the exceptions noted above.
Any enters-the-battlefield abilities of the copied creature will trigger when the token enters the battlefield. Any "as [this creature] enters the battlefield" or "[this creature] enters the battlefield with" abilities of the chosen creature will also work.
The token will still have any card types it normally has, such as creature or artifact, but it will lose any non-Alien subtypes it has, such as Human or Vehicle.
If the copied creature is copying something else, then the token enters the battlefield as whatever that creature copied, with the exceptions noted above.
The same is true for reducing the cost of Doctor spells.
Except for its name and types, the token copies exactly what was printed on the original creature and nothing else (unless that permanent is copying something else or it is a token; see below). It doesn't copy whether that creature is tapped or untapped, whether it has any counters on it or Auras and Equipment attached to it, and so on.