"ogone return empty result for $_POST content(did not return any parameter to my php result page)" Check GET parameters - they don't seem to use post when redirecting back to merchant site.
As for errors, I have been receiving error "unknown order/1/r/" in case when SHA checksum of submitted parameters was incorrect, and "rec1 not included in your account" in case when I tried to submit alias name. I haven't yet figured out how to work with aliases, for now I simply removed all alias-related parameters from my submission to Ogone and it started to work.
As for point 3 - no idea what you're talking about. Never had to enter credit card information as a merchant.
UPD: Sorry, according to Ogone FAQ error code "unknown order/1/r" means that the referer has not been configured correctly in your technical account information. For incorrect SHA checksum it's "unknown order/1/s".