Implement three functions in Python without using numpy/pandas: (1) my_min(nums) returning the minimum in O(n) time and O(1) space; (2) my_mean(nums) using a numerically stable online method (e.g., Kahan or Welford) and explaining why naive summation can be inaccurate; (3) my_median(nums) for both odd and even lengths. First provide an O(n log n) solution using sorting, then implement an O(n) expected-time solution using quickselect; discuss behavior for empty lists, presence of None/NaN, and very large integers/floats; analyze time/space complexity and worst-case pitfalls.