I think that if you want to really look at the actual acquisitional order, the more natural and longitudinal approach is by far the best. That is, a version (or slight modification of) Roger Brown's method from the late 1960s. Given that such acquisition is driven by functional and usage-based variables, an actual contextualized data set is really necessary. this is by far the most effortful of the three you suggest (corpora)...but, I believe, essential. It is interesting that the original work in EFL by Burt and Dulay did not use this method (and, I think, it resulted in the BSM) and their results were flawed as a consequence.....their acquisitional order was more an artifact of the way they collected the data than the actual order.....you don't want to make that mistake.....Of course, depending on the question you ask, data collection might vary....but for the one you propose above, this should be the way to go.
Measuring the order of morpheme acquisition enjoys a long history. To answer your question, I would like to refer you to a scholarly article by Rosansky, E.J. named: "Methods and Morphemes in Second Language Acquistion Research" whose full text is available on ERIC.
Hi! There are many research tools that you might use to measure this: discourse analysis, recorded interviews, oral performance tasks, think-aloud protocols. This depends mainly on your particular research question - and also on the nature of collected data, availability of participants, and specific circumstances of the study..But please make sure to RATIONALIZE the use of the tool or method you're going to employ - no matter what it is..You should develop an argument in which you will need to prove that this tool is the BEST choice for my research purposes...WHY??? Good luck!
As far as I know u need a longitudinal study to achieve ur aim, but based on the objectives of ur study u can choose classroom observations+recorded interviews, written recall or think-aloud approaches or treatments+ post tests(immediate and delayed ones to observe the process of the acquisition)