Because one-liners not efficient enough to solve it in time, i guess.

I thought a little between reversed and range '-1,-1,-1' and decided that reversed looks better. Of course it isn't best practice.

There is no tests to check if solution actualy preserv order of elements from the original array, because all of the test input arrays are sorted.

Your solution pass basic test, so you should now try to pass Addition Subtraction Tests. They are pretty easy to understand, because they use only basic operators without loops and stack rotations.
And only after that you should check, if your solution pass random rotation tests.

Current stack doesn't change too. You may suggest anything you like, but this is not my kata and i have never created kata)
Also you might complite original brainfck kata: https://www.codewars.com/kata/my-smallest-code-interpreter-aka-brainf-star-star-k
This kata will be much easier after that.

You definitely should not reset stack. The output string must be cleared every time the read function is called but the stacks still persist values.

Description is fine. You don't need to increment the accumulator on l command. You can check somebody else's solution.

Do you reset stack everytime read function is called?

Just finished it using Javascript. Everything works just fine.

Same problem here. Does testcases still broken?