Can undergrad students work with grad professors?
If you’re asking: can undergrads do research with professors who also teach/supervise/do research with grad students, then the answer is yes.
Most, if not all, departments make it a priority to encourage research opportunities for undergrads.
Absolutely! DS’s experience was that professors (his were CS and Math, mostly) are very open to working with undergrads. DS published a paper with a professor.
DS found the professors very approachable and encouraging.