I'm a bit surprised you did not do what you were asked to do! The problem specifically asked you to "find [itex]f'(x)[/itex], [itex]f''(x)[/itex], [itex]f'''(x)[/itex], and [itex]f^{IV}(x)[/itex] then the nth derivative but you have only found [itex]f'(x)[/itex] and [itex]f''(x)[/itex] before jumping to the nth derivative.
Other than the fact that you do not have [itex]f'''(x)= 2^3 e^{2x}[/itex] and [itex]f^{IV}(x)= 2^4e^{2x}[/itex], every thing is good!