Question: Oracle Apex 5.1, once click the button it will open new window its possible?, any one please provide the sample code

Answer: 
Use the below code

javascript:window.open('f?p=&APP\_ID.:1:&SESSION.:::1:P1\_ID:'+$v("P844\_ID")+','\_blank');
LMGTFY - Did you try the following

[APEX open URL in new window](http://www.inside-oracle-apex.com/opening-url-in-new-window/)