What is wrong with these Shell scripts?

1.  
    
   # list files given in the argument:
   
   ls$1 
    
   

2. 
   # what caused this do you think?
     
   Echo "some text" 
    
   Ls -al 
    
   

3. 
   # list all files on disk, collect results in some output file:
   
   cd /
   ls -alR > outputfile.log
   
   

4. 
   # substitute new text for old text in a number of files:
   
   read OLDTEXT
   read NEWTEXT
   
   for i in $* 
   do 
    sed -e "s|$OLDTEXT|$NEWTEXT|g" $i > $i 
   done 
   
   

5.  
   # how do I know this script has never been run?
   
   find .   -name $1    > /dev/null 2> /dev /null
   
   

6. 
   # how do I know this script has never been run?
   
   echo "enter old text" 
   read OLDTEXT 
    
   echo "enter new text 
   read NEWTEXT