All that remains is to stop the game after 10 goes - something like this:

function remove_move(el) {
  el.classList.remove('move');
  if (g_n<10) Show('buttons');
}
function button_click(colr) {
  Hide('buttons');
  g_n++;
  if (g_cards[1]==g_cards[4]) {
    if (colr=='green') g_score++;
  } else {
    if (colr=='red') g_score++;
  }
  show_card(1);
  show_card(4);
  if (g_n==10) {
    finale();
  } else {
    // wait two seconds
    setTimeout(button_click2,2000);
  }
}
...

For the finale I propose we just report on the score so we'll need a div for that - let's give it an id of finale and move it up so that it replaces the buttons.