Firstly, strikethrough is commonly used to remove data that you want to be seen. If you wish to perform this task, press the abc icon with a line directly through the middle of the 3 letters. For example, Game of Thrones is the best show on tv a great show.
Subscript will slightly lower the text from the standard line and commonly used in formulas and mathematical expressions. To add a subscript to your work, press the icon with an x2 this will make all the new text in subscript form and will not change the existing text. For example, Water is H2O, with a subscript H2O.
Superscript works in the opposite way to subscript and the text will be slightly above the standard line, this is also commonly used in mathematical expressions and specifications of chemical compounds. Look for the icon that appears as x2, pressing on this icon will raise all new text to the superscript line. The existing text will remain the same. For example, 1st 2nd 3rd.