A:AnswerYou certainly can but this computer does not have specs near good enough to run a game like The Sims 4. You would need a computer with atleast 8GB RAM and an Intel i3 processor. Even then you will only get just basic performance.
A:AnswerYou can add an SD card but the best bet is to reformat it or go through the file manager and remove all the larger files you have added. As the name of the HP Stream implies, it is mainly designed for streaming videos and cloud storage.