Also can we access ORC table stored in Hive metastore in Impala.
I think its unsupported- http://www.cloudera.com/documentation/enterprise/latest/topics/impala_file_formats.html
Impala supports RCFile but as of CDH 5.7 which is the latest at the time of writing there is no support for ORC.
In Hulu, we have supported ORC format in our branch of Impala. We're planning to contribute it to the community. Please track this: https://issues.apache.org/jira/browse/IMPALA-5717