For example, if my parent tells me to not play video games when I was a small child, is it still wajib to obey that command now that I am an adult and they have passed away when I was still a child?
What parents command to a small child is usually not meant to be valid for ever.
Parents will usually reduce their influence when a child enters the age of maturity. A grown-up person should in general be responsible and decide on his own; the parents would only command something they consider important enough at this situation. If they deceeded, they cannot decide any more, and the grown-up person is fully responsible to decide what to do.
Only God's commands can be eternally valid (and even some of His commands only refer to a certain situation or time).