Have a look at your spec. It contains various parts, and you can create regexes for each part independently. Then you just have to put them together (in the right order).

• Now I want to put some more restriction that this string should contain something or nothing in double quote in the end

  \".*?\"$
  [download]

• then some characters then ending with double quotes

  .*?\"
  [download]

• string starting with date then white space

  you already have that part in your regex
  [download]

HTH, Rata

P.S. be careful not to check for \" twice when combining the regexes ;-)