How to hide: date, tags, and category in single item view

To hide that meta block (right sidebar), you have to use custom CSS (Template Options > Custom Code > Custom CSS > copy & paste > Save & Close):

.sp-simpleportfolio .sp-simpleportfolio-meta {display: none; width:0%;} 
.sp-simpleportfolio .sp-simpleportfolio-description, 
.sp-simpleportfolio.sp-simpleportfolio-view-item .sp-simpleportfolio-details .sp-simpleportfolio-description{
  width: 100% !important; float: none;}

How to hide date and tags only

If you decided to hide only the Date and Tag block, you also have to use custom CSS:

.sp-simpleportfolio-created,
sp-simpleportfolio-tags {display: none;}