If you mean around their neck its because that where there mums pick them up when they are little.
No
the flabby bit at the top of your legs (butt)
Un-altered male cats are called Tom Cats.
No. No Flabby Jack.
Like people, kittens have different personalities. When young, they all are a bit playful but if you want an active cat, play around with them, a calm cat, watch what they do. It all depends on what you want from your kitten!
I have a male black kitten and I named it Leo but his full name is Leonardo. Give your kitten a name that you'll be comfortable with for a long time. The kitten won't worry about it. There are no rules (shoulds).
Yes
Trying to establish dominance.
no
Killer is a cute name for a kitten. If the kitten is a male, you could name it King.
He had flabby thighs.
Difference between direct access and random access