I am a marketing major that is graduating in a year. Is it legal to create...?

[No Job No Experience]

Is it legal to create marketing materials to beef up your resume?

Lets say it was posters and videos; would I get in trouble for using copyrighted items such as logos and trademarks to create something an advertising agency might create? I have some background in web design and filming and editing videos and would like to know if the below scenarios are viable.

Example: Diet Pepsi. I like drinking Diet Pepsi and would create a 30 second "TV commercial" that I think a typical advertising agency would produce (although on a much lower budget and scale)

Example 2: Video games. Lets say a new highly anticipated video game will be coming out and I then go and create a typical 1 page magazine advertisement for it.

Question 1: Is it okay for me to do both?
Question 2: What if I decided to upload both the video and poster to media sites such as facebook, youtube, and my own personal website (like in a list of "fake ads" I've made)
Question 3: I know credit should be given where credit is due, so if I clearly state that I do not own any of the copyrights and trademarked terms in both the videos/posters/websites somewhere, would that be ok?
Question 4: Is there a correct term for what I want to do above? Creating fake ads to showcase my creative talents.

Sorry for the lengthy question, but times are hard and jobs are scarce...companies only seem to want to hire high gpa / Ivy league students or even accomplished professionals for entry level positions. I thought by doing this, I may have a stronger resume and be more competitive for an internship! Thanks in advance!