dynamically change uitableviewcell or uitableview in ios objectivec

I am working on a project where i need to show the users activity. The activity will have images and texts

user can write a comment on the activity.

I am trying to implement this on uitableview. As i am not sure where to study the uitableview as online tuts will only give the basic usages.

If anyone can suggest how to implement this(doesn't necessarily using tableview as so far i can think of tableview only) will be great help.

So if I am implementing this using tableview i need to change the cell dynamically. for a simple experiment i tried

NSIndexPath *indexPath = [NSIndexPath indexPathForRow:1 inSection:1] ;
UITableViewCell * cell = [self.tableView cellForRowAtIndexPath:indexPath];
UIView * commentView = [[UIView alloc] initWithFrame:CGRectMake(0,0,cell.frame.size.width,cell.frame.size.height)];
[commentView setBackgroundColor:[UIColor blueColor]];
[cell addSubview:commentView];

but nothing is changing.