WCF Asynchronous Services and WebHTTPBinding

Hi
I am a newbie to WCF. I have 2 questions regarding WCF services which
are however at the advanced level.
I am using REST style invocation for my services. My service name is
GetData and it would be used by generic AJAX clients and/or ASP.NET
AJAX clients.
1. Using the URL, it is possible to invoke the service (REST style).
But is it possible to invoke the Asynchronous version of my method
i.e. BeginGetData(). I believe not, since there is no proxy involved
here.

2. Can I use WebHTTPBinding to maintain state the way ASP.Net does and
to enable reliable messaging, security and ordered delivery for my
communication? By default, I know that WebHTTPBinding does not support
these. Is there a way to customize these?

Kindly reply asap as I am already delayed on my design.

Thanks in advance
VIkas Manghani