It is still a child. I don’t think it translates
1:1 with human aging, but this species has a particularly long infancy-early childhood stage.There might be something unique to the Yoda species regarding Force sensitivity, but it’s already been established in canon that Force-sensitive babies in general have a predisposition to using the Force, regardless of species. The idea being, I’m assuming, that babies and young children lack some of the qualities that adults have that can hold back their ability to use the Force (like doubt or disbelief). And it is possible that the time he spends in this young childhood stage plays a part in why he can lift a mudhorn vs a toy ball.
This exactly. There’s a lot of evidence from the movies (especially the prequels) which points to early training as extremely important in developing skill in the Force, and I think you’re right that it has to do with the lack of a rigid experiential framework present in adults. So if the Yoda species has this super long developmental period, it stands to reason that most of the members of this species would gain some Force abilities. I imagine it could be something like 50% or more of the species would have this ability into adulthood, while for humans that percentage would be far less because of how rapidly they progress through infancy. Of course, I doubt that baby Yoda could really control the Force or plan to use it in advance.
There’s also the angle of hereditary Force sensitivity, and it may be that Yoda’s species is essentially just one family, that is if their method of reproduction is different enough to avoid the effects of inbreeding.
It’s an interesting question.