Please check if you are getting same call_user_func() error in demos. If yes, let me know your php version. If not, you can verify your code by comparing with demo.

For jquery conflict, i would recommend to include jquery migrate plugin. It make jquery versions compatible.
http://blog.jquery.com/2013/05/08/jquery-migrate-1-2-1-released/

Hi,
The jquery I am using is 1.8.3 the same one as grid's jquery, can I use my jquery instead of grid's?
If I remove it will it affect the grid's working?
As per my observation the date picker is the only thing that has the issue.

As per the set_event() the error is not there in demo, only when I call it in the code it gives me the following error,

$e["on_update"] = array("update_data","",true);
$e["on_clone"] = array("custom_clone1", "null", false);
$e["on_data_display"] = array("filter_display1", "null");

$g->set_events($e);
when I uncomment the above line.

Warning: call_user_func() expects parameter 1 to be a valid callback, class 'null' not found in C:wampwww..phpgridlibincjqgrid_dist.php on line 1946

Fatal error: Cannot break/continue 1 level in C:wampwww..phpgridlibincjqgrid_dist.php on line 1951

The datepicker js code is in jqurey-ui.custom.min.js. It should not conflict with jquery core if you have same versions.
You can also compare the jquery core js files.

For set_events() error, the issue is perhaps, "null" null with string.

In php, null is used without string.

Either remove " " from null, or make it empty string "". It should work after that.

$e["on_clone"] = array("custom_clone1", "", false);
$e["on_data_display"] = array("filter_display1", "");