I'll evaluate each exercise file separately since they appear to be different problems.

Exercise_1.py (Stack implementation using list):
Strengths:

• The basic structure of a stack is implemented with common operations: push, pop, peek, size, isEmpty, and show.
• The isEmpty method correctly checks if the stack is empty by checking the length.

Areas for improvement:

1. The isEmpty method should return a boolean (True/False) rather than returning the stack itself when empty. Currently, it returns the empty stack (which is truthy in Python) instead of False.
2. The show method is incorrect. It returns the first element immediately instead of showing all elements. It should return the entire stack or print it.
3. There's no time and space complexity comment at the top as requested.
4. The pop method could cause an IndexError if called on an empty stack. It should handle this case.
5. The peek method could cause an IndexError if called on an empty stack.
6. The init method should initialize the stack as an empty list, which is correct.

Time Complexity:

• push: O(1) amortized (due to list append)
• pop: O(1)
• peek: O(1)
• size: O(1)
• isEmpty: O(1)
• show: O(n) but currently implemented incorrectly

Space Complexity: O(n) where n is the number of elements in the stack.

Exercise_2.py (Stack implementation using linked list - but incorrect):
Strengths:

• The structure of a Node class is correct.
• The menu-driven interface for stack operations is provided.

Areas for improvement:

1. The Stack class incorrectly uses a list instead of a linked list. The problem likely expects a linked list implementation.
2. The push method uses "self.append(data)" which is not defined. It should add to the head of the linked list for O(1) time.
3. The pop method uses "self.pop()" which would cause infinite recursion. It should remove from the head.
4. There's no reference to the head node in the Stack class.
5. The Stack class doesn't maintain the linked list structure; it uses a list which defeats the purpose.
6. The pop method doesn't handle empty stack cases properly.

This implementation is fundamentally incorrect for a linked list-based stack.

Exercise_3.py (Singly linked list implementation):
Strengths:

• The basic structure of a singly linked list with append, find, and remove methods is attempted.
• The Node class (ListNode) is correctly defined.

Areas for improvement:

1. The append method has issues:
   • It creates a new node but doesn't correctly handle the case when the list is empty (the while loop will fail if head is None).
   • It should check if head is None and set head to the new node, then return.
   • The current code sets curr to self.head but then doesn't traverse correctly to the end.
2. The find method:
   • It never advances the curr pointer, so it will infinite loop if the head doesn't match the key.
   • It should advance curr in the loop: curr = curr.next.
3. The remove method:
   • It has several issues:
     • It compares self.head == key (should be self.head.data == key).
     • It doesn't handle the case when the key is not found.
     • The while loop condition is curr.next != None, which means the last node is never checked for key.
     • The pointer advancement inside the loop is not correct; it should advance only if no removal occurs.
4. The ListNode init method sets self.next to None, overriding the next parameter. It should be self.next = next.

Time Complexity:

• append: O(n) - correct but implementation is broken
• find: O(n) - but currently infinite loops
• remove: O(n) - but implementation is broken

Space Complexity: O(n) for n elements.

General feedback across all files:

• The code lacks comments and documentation. The problem asks to include Time and Space complexity at the top of each file.
• There are several syntax and logical errors that would prevent the code from running correctly.
• The student seems to have misunderstood the linked list implementation in Exercise_2 and Exercise_3.
• Edge cases (empty stack/list, operations on empty structures) are not handled properly.

Let me evaluate each exercise file separately:

Exercise_1.py (Stack implementation using list):
Strengths:

• The basic structure of a stack is implemented with push, pop, isEmpty, peek, size, and show methods.
• The isEmpty method correctly checks if the stack is empty by checking the length.

Areas for improvement:

1. The isEmpty method should return a boolean (True/False) rather than returning the stack itself when empty.
2. The show method currently returns only the first element because of the return statement in the loop. It should instead return the entire stack or print it.
3. There's no time/space complexity comment at the top as requested.
4. The peek method could have an issue if the stack is empty - it should handle that case.
5. The test code pushes strings '1' and '2' but the problem might expect integers.

Time Complexity:

• push: O(1) amortized (same as list append)
• pop: O(1)
• peek: O(1)
• size: O(1)
• isEmpty: O(1)

Space Complexity: O(n) where n is the number of elements in the stack.

Exercise_2.py (Stack implementation using linked list - but incorrect):
Strengths:

• Has the basic structure with Node class and Stack class.
• Includes a user interface for testing.

Areas for improvement:

1. The Stack class incorrectly uses a list instead of implementing a linked list. The push and pop methods are calling list methods (append and pop) rather than manipulating nodes.
2. The Stack should maintain a head pointer instead of a list.
3. The pop method doesn't handle the case when the stack is empty (would throw an exception).
4. The user interface expects operations but the implementation doesn't match the linked list concept.

This implementation is fundamentally incorrect as it uses a list internally instead of actually implementing a linked list stack.

Exercise_3.py (Singly linked list implementation):
Strengths:

• Has the basic structure with ListNode and SinglyLinkedList classes.
• Implements append, find, and remove methods.

Areas for improvement:

1. In the append method:
   • The new node's next should be set to None explicitly.
   • There's a logical error: if the list is empty, it sets self.head to new but then continues to traverse, which will cause an error since curr would be None.
   • It should handle the empty list case separately and return after setting head.
2. In the find method:
   • The while loop doesn't advance the current pointer (infinite loop).
   • Should return None if the key is not found after traversing the whole list.
3. In the remove method:
   • The condition if self.head == key should compare data, not the node with key.
   • The while loop condition should be while curr is not None rather than while curr.next != None to avoid missing the last node.
   • The pointer advancement should happen in each iteration, not only when a match is found.
4. No time/space complexity comments as requested.

General issues across all files:

• Missing comments about time and space complexity as requested in the problem.
• Some methods don't handle edge cases (empty stack/list).
• Inconsistent formatting and some syntax issues.