Now I am 60years old and I want to say that sometime in the past i was at Oxford university 5 years for example but without a specific time in the past,30 or 40years ago etc.

1. "i have studied at Oxford for 5 years" this means 5 last years till now,correct?

But what should I say in scenario above?Which one is correct?

2. "I studied at Oxford 5 years (for 5 years)"

3. "I was studying at Oxford 5 years (for 5 years)"

Now I am 60 years old and I want to say that sometime in the past I was at Oxford university 5 years for example but without a specific time in the past, 30 or 40years ago etc.

1. "I have studied at Oxford for 5 years" this means 5 last years till now, correct?

But what should I say in scenario above? Which one is correct?

2. "I studied at Oxford 5 years (for 5 years)"

3. "I was studying at Oxford 5 years (for 5 years)"