I am trying to figure out how to use the word however in a sentence. Could someone explain the differences of beneath stated sentences?
For example:
1. I like fast food, however, it is not healthy to eat fast food every day.
2. I like fast food, however. It is not healthy to eat fast food every day.
3. I like fast food. However, it is not healthy to eat fast food every day.
4. I like fast food. It is, however, not healthy to eat fast food every day.
So if I would write the above stated sentence in a essay I would have chosen option 2 and 4. Those sentences sound correct in my opinion. However, I often see option 1 and 4 in written English. I am not sure if I used 'however' in the correct way but that is how I see how people uses however.
I am not sure if the following is correct, but I also sometimes see that however is used at the end of a sentence. Like: I like fast food, it is not healthy to eat fast food every day, however.
But I think the last example cannot be correct.

Thanks in advance.