To set the record straight:
Codeblock 0 is deprecated (not non existent) If there are data stored in codeblock 0 it will be available (there will be a tab for it) and editable. You will also get the codeblock 0 deprecated message.
The only way to clear this is to remove any content from codeblock 0. If this is not working you need to examine your error logs to find what is failing.
so what can be trick to appear old way listing in frontend ? as currently I see at end of source code of page which is I think some way the code is breaking and not completing the html rendering.
Sorry but am no programmer so dont understand just had this functionality working on previous version theme and zenphoto both.
Please guide.
Seeing the is an indication that the text has been html encoded (a normal procedure for handling arbitrary text.) If this is still about the codeblock text you quote originally, the did not come from the codeblock.
Regrettably, if you wish to use a feature you have to acquire the need knowledge. At any rate, save for the deprecation of codeblock zero there has not been changes in codeblock handling.