Yes. All it takes to move teeth is a little bit of pressure and a lot of time. If someone sucks their thumb for enough hours of the day they will cause the upper front teeth to shift.
Absolutely. Thumb or finger sucking beyond 4th b'day can lead to skeletal malformation and dental malocclusion. Please see pediatric dentist or orthodontist for evaluation and advice.
You'll need ortho! Yes, thumbsucking can and will affect your teeth. The pressure from both the presence of the thumb in the mouth and the sucking action will cause your teeth to shift and potentially affect your occlusion (or bite).