As for question one, what you said earlier was a bit general and not easy to answer. Are you asking about the technical problem to be solved or your technical solution? I feel that what you wrote later also somewhat combined the two. were mixed together.
For question 2, it may depend on the situation. If "Device A has at least one terminal" is one of your innovation points, and it is very likely that you will have to fall back to this when responding to comments in the future. Above, I think it is better to give two or three embodiments, one for one terminal and one for two terminals, otherwise there may be support problems. If it is not the innovation point, but some common methods in actual use, it can be simpler. But if it doesn’t bother you, it’s best to write in detail.
For question three, the use of drawings is to more clearly demonstrate your technical solution. If the description is clear enough, it does not need to be included (except for utility models). But if (part number) appears in your text description, then the attached drawing must be included. As for the importance of adding pictures, as mentioned above, it depends on whether this is your innovation point.
For question four, generally speaking, the beneficial effects of mechanical structures can only be mentioned at the end. There is no need to analyze in detail why they bring about what kind of effects, but this is all because of the The description of the structure basically means that anyone who makes machinery can imagine these effects. If it is difficult for a person skilled in the art to imagine the technical effects brought about or the technical problems to be solved from your description of the structure. That may be a problem of insufficient disclosure.