I'm a little confused by your question. I think of a backspace key as being a key that when pressed deletes the character that precedes the cursor, and moves the cursor one character to the left (This key usually sits on the upper right corner of a computer keyboard). This function is provided on the touch by the button you described as the 'backspace delete'. In Safari it sits above the 'go' button, in notes it sits above the 'return' button.
If the function you want is to move back a character without deleting, I think the button that provides that on a standard keyboard is usually called a left arrow key, and on a touch doesn't exist because you can just touch the spot within the text you'd like to begin typing from. For fine selection, hold the spot you'd like to begin typing from and a magnifying glass will pop up to help you move the cursor into place.
