No. Unless it is an open question (e.g. with what, who, why e.t.c.), there is no way to tell a question from a statement, apart from the presence of a question mark (when reading), or tone of voice (when speaking).

Because "сад" is a masculine noun. I suggest you to read Tips&Notes.

Yes, чий is masculine, чия is feminine.

See the question by Butterflys_Dust and the corresponding answers.