Where i can download older versions of Firefox Browser?

ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases

Can I turn autocomplete ON/OFF programmatically?

As a web developer you *cannot* turn this feature ON programmatically if the user has turned it OFF. That is not allowed.

However, if needed, a web developer can turn this feature OFF either for a particular field or for the entire form like below.

<input name="name" autocomplete="OFF" type="text">

<form autocomplete="OFF">