Excel does not have the functionality to sort by custom lists because it is primarily designed for numerical and alphabetical data sorting. Custom lists are specific to individual users and may not be relevant or useful for everyone. Additionally, implementing custom list sorting could complicate the sorting process and make it less intuitive for users. Excel focuses on providing a user-friendly and efficient experience for common data sorting needs. **

Among the three sorting algorithms, Insertion Sort is generally considered better in terms of performance. This is because Insertion Sort has an average time complexity of O(n^2), which is better than the average time complexity of O(n^2) for both Selection Sort and Bubble Sort. Additionally, Insertion Sort is more efficient when dealing with small datasets, as it has a relatively low overhead. Overall, Insertion Sort is often preferred over Selection Sort and Bubble Sort for its better average time complexity and efficiency with small datasets. **

Selection Sort has the advantage of being simple to implement and having a consistent time complexity of O(n^2) regardless of the input data. However, it is not efficient for large datasets due to its quadratic time complexity. On the other hand, Insertion Sort is efficient for small datasets and nearly sorted arrays, with a best-case time complexity of O(n). However, it also has a worst-case time complexity of O(n^2) and is not suitable for large datasets. **

The runtime of Insertion Sort in the worst case is O(n^2), where n is the number of elements in the array. This is because in the worst case scenario, each element needs to be compared and shifted to its correct position in the sorted array, resulting in a quadratic time complexity. Count Sort, on the other hand, has a linear runtime of O(n+k) in the worst case, where k is the range of the input values. This is because Count Sort creates a count array to store the frequency of each element, and then iterates through this count array to reconstruct the sorted array. **

Insertion sort works by iterating through the array from left to right, comparing each element to the elements on its left and inserting it into the correct position in the sorted portion of the array. It starts with the second element and compares it to the first element, then moves to the third element and compares it to the elements on its left until it finds its correct position. This process continues until all elements are in their correct positions, resulting in a sorted array. Insertion sort has a time complexity of O(n^2) in the worst-case scenario. **

To sort alphabetically, you can simply arrange the items in the list or data set in alphabetical order from A to Z. If you are working with a computer program or software, there is usually an option to sort alphabetically that you can select. In most cases, you can sort alphabetically by clicking on the column header of the data you want to sort or by using the sort function provided in the program. **

Insertion Sort works by iterating through an array and comparing each element with the elements before it. It starts with the second element and checks if it is smaller than the element before it. If it is, the two elements are swapped. This process is repeated for each element in the array, gradually building a sorted portion of the array from left to right. The algorithm continues until all elements are in their correct sorted positions. **

Merge Sort works by dividing the unsorted list into smaller sublists, sorting those sublists recursively, and then merging them back together in the correct order. This process continues until the entire list is sorted. The key step in Merge Sort is the merging process, where the sorted sublists are combined in a way that maintains the order of the elements. This algorithm is efficient and has a time complexity of O(n log n) in the worst-case scenario. **