Questions on the Categorical Imperative

a) How can we make sense on the type of contradiction that arises?
Logical, teleological or practical contradiction
-> In the different examples, Kant operates with different formulas of the Categorical Imperative (universal law, law of nature) and there seems to be different types of contradictions (e.g. the suicide example and the borrowing money example)
b) Kant would not tolerate different outcomes when running the different formulas of the Categorical Imperative. How can we make sense of that?
c) How general should a maxim be? (e.g. the example of "Jim and the Indians")