As an altar server, does one still fufil the Sunday obligation?
Are you asking if serving Mass on Sunday as an altar server meets the obligation to attend Mass on Sunday?
If so, yes, attending Mass on Sunday (or the Saturday Vigil) while serving Mass at the altar meets the obligation.
Yes of course it does. Just as being a reader, EMHC, choir member, or usher would fulfill the obligation.
Why do you think it wouldn’t?