HTTP_REQUEST and HTTP::redirect and HTTP::respond with if condition and source IP

Comments inline:

Extent result. when using /use1/ Browser Result - The webpage cannot be found 404

A request for /use1/ should result in a redirect to "https://ecr.host.com.qa/use/", which (because there's no condition for it) goes to the Default condition and should display some HTML content. Is this iRule applied to the "https://ecr.host.com.qa" URL? Does the "/use/" URI actually exist on this server?

when using /use2/ Browser Result - Blank, nothing displayed.

Assuming you are still seeing the log message for the correct condition, the response you're sending isn't properly formatted as XML data. Your browser may be blocking it. If you try this from a cURL statement, you may see different results:

curl -k https://x.x.x.x/use2/

when using /oncfo2/ Browser Result - Blank Page, nothing displayed.

Same as above.

when using /oncres2/ Browser Result - Blank Page, nothing displayed.

Same as above.

when using /oncres1/ Browser Result - redirected to https://.../oncres/...working. Error 403--Forbidden

That's certainly going to be an application issue.