Glad to meet you, native English speakers, but sorry to disturb you due to my queries still about one sentence related to the same meaning.
1. He resigned as manager after eight years.
2. He resigned as a manager after eight years.
3. He resigned the position of manager after eight years.
4. As a manager, He resigned after eight years.
5. As a manager, He resigned his position after eight years.
Question:
Which is grammatically correct?
Do they all have the same meaning?