Yes I have found the chair works well as Dr Kennedy states, most kids will get off but you frimly put her back even if it takes a while.,they dont usually sit there ,after a few mins they get fed up and go quiet. I have known Moms who do it with a bean Bag, and take it on vacation so it is around where ever you are.Her speech and Language ought to be looked into toaswell.At 2 possibly it is her way of communicating excitement at the Ads, are they any particular Ads are they Noisy Ads,Singing Ads,By the way kids often flush the Loo a lot its fun to them, ease off a bit.
Relative to the screaming, two things should occur. You should arrange evaluations with both Speech/Language and Occupational Therapy clinicians. Second, from a management perspective, she is too young to be placed in her room for time out. She should sit in a time out chair (adult size). Immediately when she begins to scream, place her in the chair, saying 'No screaming'. She should remain in the chair for five minutes, and the time should commence only when she is quiet (use a digital cooking timer to track the time). Read Lynn Clark's book SOS Help for Parents - it will give you additional guidance re: managing behavior.
sorry I didn't complete remember you whole story once I got typing but in short I watch super nanny as well as meor the dog. they use all of the techniques that has worked for me (I also have two childern ten years apart one has ADD and the other has ADHD/bipolar 1, I,ve not had to yell or hit, repeat yes.(not repeat, rephrase the teachers though the years liked using my method and was real easy once everyone was on board) my boys are now 25 and 15 most of our life has been stressfree. if youyell at a dog for backing it just thinks you're playing same for a child except negative attention is still attention .
when unexceptable behavior happens, I would put them in time out with a stop watch . and they have to be quiet for as many minutes as years of their age. If they make a sound before time is up, time starts all over again. it worked great for me. (don't use angry looks,sad works as well as it gets more positive results as it is with adults) in the case with the screaming. i would just stop what I was doing, and sit on the floor and do the same thing. they stop and look at you .( of course this you won't do in the middle of a resturant.in this case take out to the car or just outside and wait til they calm down.then tell that you can't be inside either because someone has to sit with them. keep doing these things until they get it. if any of this helped I'd like to know, so far everyone I teach this to, had great success good luck