We have double-spaced here for readability, but CSE style does not specify a preferred line spacing in bibliographies. Instead, this decision is left at the publisher's (or your professor's) discretion.
Citations are presented in the order in which they are introduced in the text. This means that the work that is cited first in the text (and thus assigned the number "1") appears in the list first, the work assigned the number "2" appears next, and so on.
Your bibliography should contain only those works that correspond to a citation in the body of your paper. If you wish to include additional references not cited in your paper, you may provide another list with the title "Additional Reading" or similar.