Question: is response.redirect always an http GET response? or it could be POST?....

Answer: 
A redirect is an Http response sent to the client. The response contains an Http Header called Location which must contain an absolute url. 

The client then issues a GET request against this url.

So, no, POST is not an option.

More details here: <http://en.wikipedia.org/wiki/URL_redirection>
Response.redirect uses only GET..It can't be a post..And in between what is the language?