Your 2nd sed search pattern is still wrong. Even the first is wrong if you ask me. It works for you by chance.
sed -e '/\<following/>/d' /home/BSD.txt > /home/BSD_DELETE.txt sed -e 's/\<from\>/their/g' /home/BSD.txt > /home/BSD_REPLACE.txt
If you are asked to work on words you have to use word boundaries in the search pattern.
<\word\> (universal) or
<\bword\b> GNU sed only.
I tried the above and it is failed too
If you just copied it without adjusting it for the specific task requirement, yes, most probably the task will fail