Is it possible to put in my portfolio the works that I made according to the psd layouts found on the Internet?

Question

Freelance

Or does it have to be real work done for the customer?

Answer 1

For a portfolio, there is no fundamental difference if there are 10 or 100 completed projects, the main thing is that you will show how complex these projects are, how much they show your layout skill.
Also remember that skillful layout is certainly an important skill, but far from the only one for the front-end.
Consider other projects in your portfolio as well. Look at this development map, think about what skills you lack: https://roadmap.sh/frontend

Answer 2

Can.

Answer 3

Question 1: who will check?
Question 2: what's the difference whether the project is real or not? You made it up, your skills are visible.

Answer 4

Drop what's stopping you