Can traveling while an I-485 is pending affect unlawful presence or prior immigration violations?

Yes, travel can sometimes trigger complications if the applicant previously accumulated unlawful presence before filing for adjustment of status. For example, departing the United States after accruing significant unlawful presence may activate three-year or ten-year reentry bars. In those situations, even if the person has Advance Parole, leaving the country could still create immigration consequences depending on the individual’s history. Because every case is different, individuals with prior overstays, removal orders, or other violations should consult an immigration attorney before traveling internationally while their adjustment of status is pending.

Yes it can, because USCIS may treat the I-485 application as abandoned.