If 2 and 3 have commas instead of periods after "home," they would be the origins of #1, yes. An alternative for #1 is "At home, I went online ... "
#4 would not be used with the word "Being" but if that word were removed, the sentence would be fine.
1. Back home, I went online and found the recipe.
2. When I was back home. I went online and found the recipe.
3. After I was back home. I went online and found the recipe.
4. (Being) back home. I went online and found the recipe.
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Does #1 come from #2 or #3?
Is 'being' deleted before 'Back'?
3 answers
1. Back home, I went online and found the recipe.
2. When I was back home, I went online and found the recipe.
3. After I was back home, I went online and found the recipe.
4. (Being) back home, I went online and found the recipe.
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Does #1 come from #2 or #3?
Is 'being' deleted before 'Back'?
2. When I was back home, I went online and found the recipe.
3. After I was back home, I went online and found the recipe.
4. (Being) back home, I went online and found the recipe.
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Does #1 come from #2 or #3?
Is 'being' deleted before 'Back'?
Does #1 come from #2 or #3? Yes -- from either or both.
Is 'being' deleted before 'Back'? Yes, it needs to be deleted.
Is 'being' deleted before 'Back'? Yes, it needs to be deleted.