Thanks for your feedback. Function argument having a uint type rules out the negative indexes. Trying to pass a negative number as a uint would not event reach a contract, it would fail on hardhat level. However I admit that I do not check if the user has modified any of the required method signatures by e.g. changing the uint to int. Added the test checking if the interface is left unmodified.

Of course. Fixed.

Thanks for the feedback, added some additional tests, also for the case of getting an item with a non-existing index.