Words that you can use other than witnessed are seen, observed, watched, viewed, and noticed. These are synonyms of witnessed.
I witnessed a murder.
Jellybeans 2010
It depends on the context or sentence. The next word could be "than" if used to compare two things, or it could be any other word depending on the sentence structure.
It is a foster child, but one word could be adoptee.
Other than strengthen, the word could be reinforce, fortify, boost, or toughen.
witness/ witnessed observe/observed
We've just witnessed a miracle.
I cannot think of any way the word 'everywhere' could be used other than as an adverb.
The Arabic word for God, other than Allah, is "Ilah."
A synonym for "you" could be "one" or "they" depending on the context of the sentence.
"Storage" is a word that rhymes with "cartage" other than "garbage."
Ghee, oil, oleo, shortening are the other words which could replace the word butter or margarine.