I am planning to go to UK and visit European countries on visitor visa, can we apply visa simultaneously in one application ?
Once you get your UK multiple-entry visa, you can use it to go to Ireland (including Northern Ireland) and Scotland. But, you can NOT use it to enter Schengen countries. You will need to apply for Schengen visa separately. See Main Destination to apply for Schengen visa - Indian Citizen to determine which consulate you should apply for a Schengen visa.