Answer to Question 1
An experiment with this design would include 120 conditions. That would mean that, with a between groups design, you would need 120 people to provide a single person in each condition, and you would never want a single person. If you wanted 10 people, which is still small, it would involve 1,200 people. If you used a repeated measures design, each person could in the extreme, be involved with 120 conditions, which wouldn't be practical.
In addition, it could be very difficult to interpret the interactions, especially if there were higher order interactions (e.g., three- or four-way interactions).
Answer to Question 2
Research conducted in established or commonly accepted educational settings, involving normal educational practices can be exempt from approval, such as the effects of different instructional strategies.
Research involving the use of educational tests, survey procedures, interview procedures or observation of public behavior. (Surveys and interviews on sensitive or controversial topics may require IRB approval, though.)
In addition, research involving public officials or political candidates can be exempt from IRB approval.
Research involving the collection or study of existing, publicly available data, documents, records, pathological specimens, or diagnostic specimens is exempt if the personal identity of those providing the data is protected.
An example of an experiment that supported Beadle and Tatum's one gene
Desert shrubs create distinctive thermal microclimates in the desert landscape
The Meselson-Stahl Experiment
Computed tomography (CT) uses X-rays to create a CT scan of the brain.
Kyoto Protocol encourages industry to innovate and reduce the level of emissions
Share of Hours Worked by Education Level, 1940–2008