Questions with some usages of で


From my understanding, "で" have many different usages in Japanese. I have some
questions regarding the following particular uses of で. It would be very
helpful if someone could also come up with other sentence examples related to
my questions. Thank you.

1) 皆 **で** 写真を撮ります。

  * What is the meaning of **で** here? Does it sort of indicate "状態" to mean taking a picture of everyone " _as a group_ "? I'd appreciate if someone could also come up with another sentence or two where **で** also served as the same purpose as we have in this example.

  * If for example, there are a total of 9 people in the group and it was decided that we will take a total of three pictures with 3 different people in each picture. In this case, can one say 三人 **で** 写真を撮ります？ If it is incorrect, what are more appropriate ways to say this?

2) In general, we hear people say "二人 **で** ", is the usage of **で** here the
same as **で** in the previous question?(i.e.皆 **で** 写真を撮ります)

3) Upon entering restaurant, when waiter asks how many people in the group,
can one say "二人 **で** " if there are two people? Is this **で** usage the same
as in my previous two questions?

4) I learned that **で** is also used when _specifying a choice from a limited
number of selections_ such as when we buy clothes, we can say 大 **で** to
specify size "large".

  * My question is, I remember hearing people say "こっち” **で** when they tell the salesperson of a particular item they want to buy. Why do they also use **で** here? Is the usage of **で** here indicating "こっち” is the particular item chosen to buy "from the entire selections of clothes in the store"?




1) and 2) are the same and answers already exist
[here](https://japanese.stackexchange.com/questions/8107/particle-%E3%81%A7%E3%80%80versus-
particle%E3%80%80%E3%81%A8) and
[here](https://japanese.stackexchange.com/questions/9730/can-
particle-%E3%81%A8-and-%E3%81%A7-both-mean-with?lq=1).

3) Because the waiter usually asks "何名様ですか", I usually say "二人です", but
"二人で(お願いします)" works as well, I guess.

4) "大で" is really a short way of saying "大でお願いします". Here (and everywhere
else), で is the connective form of the copula だ, which in particular implies
that the sentence is not complete.

