It is very common to hear two- and three-year-olds in English saying "I falled down," "She gived me it," etc. And the frequency of a verb form is inversely related to the age at which one is likely to master it, indeed to the point where past tenses such as "lay" and "shone" are becoming archaic in most dialects of NA English.
What does the journey of a child's acquisition of verb (or noun/adjective) forms look like in a heavily inflected language, such as
- Tundra Nenets, which inflects for subject, object, tense, and sixteen moods?
- Basque, which only has ten or fifteen inflected verbs, but they can have a thousand forms?
- Attic or Epic Greek, with its hundreds of forms and countless manifestations of suppletion and deponency? (Obviously there would be little data on L1 acquisition here, but a language with similarly many irregularities?)
- Koyukon Athabaskan (Alaska), with classificatory verbs specifying "the shape, material, consistency, size, location, arrangement, and number of their nominal arguments"?
- Polysynthetic languages, such as Mohawk?
I'm looking in particular for an analysis of which categories start to be incorporated correctly at what age, and what children do beforehand to express the same ideas. (For example, do they speak an inflected language as if it were more agglutinative?) Even a narrative of one child's journey in learning the grammar would be most welcome.