There are multiple causes for chronic nausea and vomiting. To name a few, it can be due to gastroparesis, intestinal obstruction, chemotherapy, intracranial tumors, motion sickness, migraines, hepatitis and ear issues such as benign paroxysmal positional vertigo. Evaluation of underlying cause is important to guide the appropriate treatment.

Hard to say but could be gastritis
And quite a few other reasons depends on the histpry

There are dozens and dozens of possible causes for nausea and vomiting, too many to list.
A careful history should be done to try to determine the cause. It should be noted that many of the causes are not gastrointestinal but rather may arise from other organ systems.