Major Issues While upgrading OJS 2.3.3..3 to 2.4.8.2

I was trying to upgrade from OJS 2.3.3.3 to 2.4.8 and faced many errors while upgrading.
Please help me,I am in deep trouble.

Can someone explain we what is this error?
ojs2 has produced an error Message: WARNING: assert() [function.assert]: Assertion failed In file: /home/journals/beta.journalofscience.org/lib/pkp/classes/plugins/PluginRegistry.inc.php At line: 241 Stacktrace: Server info: OS: Linux PHP Version: 5.2.17 Apache Version: N/A DB Driver: mysql
NOTICE: Undefined index: TYPE (/home/journals/beta.journalofscience.org/lib/pkp/lib/adodb/adodb-xmlschema.inc.php:282)
ojs2 has produced an error Message: WARNING: Invalid argument supplied for foreach() In file: /home/journals/beta.journalofscience.org/lib/pkp/lib/adodb/adodb-datadict.inc.php At line: 774 Stacktrace: Server info: OS: Linux PHP Version: 5.2.17 Apache Version: N/A DB Driver: mysql