How many and which prepositions do you need to express everything that prepositions can express.
In "Alice goes under the line" and "Alice goes over the line" you could solve both cases with the same proposition if you add an adjective that indicates going under or over. It either going under or going over.
The same doesn't go for prepositions such as 'of' and 'to'. You can't replace one of them with the other by adding an adjective.
Is there a minimal set of essential preposition that you can't exchange against each other?