Write an MIPS program that reads 5 integers and displays them in reversed order

Question

I have already done that, but I don't seem to understand the $sp - Stack pointer fully. As it says that the Stack Pointer $ sp should always point to the last occupied memory cell of the stack. (when I run it the $sp stays the same until the program prints then changes).

May someone please tell me what is going on with the $sp here? or what should be done exactly in order for it to execute correctly as asked for?

Here is my code:

.data
     arr: .space 20 #create array of length 5
     inputPrompt: .asciiz "Please enter a whole number: \n"
     spaceChar: .asciiz " "
     
.text
     main:
     #Prompt user to enter a whole number
     li $v0, 4
     la $a0, inputPrompt
     syscall
     
     jal while
     
     #print in reversed order
     addi $t0, $zero, 16
     jal whileOutput

   
        while:
            beq $t0, 20, exitWhile
            
            #read input
            li $v0, 5
            syscall
            
            addi $sp, $sp, -8 #make up space in stack
            sw $s0, 0($sp) 
            sw $ra, 4($sp)
            
            sw $v0, arr($t0)
            move $s0, $v0
            
            add $t0, $t0, 4
            j while
     
        exitWhile:
            jr $ra 
        
        
        
     whileOutput:
            beq $t0, -4, exitOutput

                lw $t6, arr($t0)
                
                #print Integer
                li $v0, 1
                move $a0, $t6
                syscall
        
                #print space
                li $v0, 4
                la $a0, spaceChar
                syscall
        
            addi $t0, $t0, -4
        
                j whileOutput
            
            
    exitOutput:
            #restore space in Stack
            lw $s0, 0($sp)
            lw $ra, 4($sp)
            addi $sp, $sp, 8
            
            #end program
            li $v0, 10
            syscall

     ```