Singly Linked List Reversal — Variants and Edge Cases

You are given a standard singly linked list with nodes of the form:

• Node fields: value, next
• Head pointer may be null (empty list).
• Assume 1-indexed positions for m and n.

Implement and analyze the following:

A) Reverse Entire List

1. Provide an iterative in-place solution that uses O(1) extra space.
2. Provide a recursive solution.
3. Analyze time and space complexity of both.
4. Explicitly handle edge cases: empty list, single-node list, and very long lists (stack depth considerations for recursion).

B) Reverse a Sublist [m, n]

• Reverse the nodes from position m to n (inclusive), in-place, and return the head. Assume 1 ≤ m ≤ n ≤ length of list.

C) Reverse Nodes in k-Groups

• Reverse the list in contiguous groups of size k using O(1) extra space. If the final group has fewer than k nodes, leave that tail group as-is.

D) Cycle Detection Before Reversal

• Explain and implement how to detect a cycle in the list and reject (do not attempt to reverse) if a cycle is present.

You may use pseudo-code or code in a language of your choice.