He is responsible for his own actions.
2. He sent me a message. ,or
He sent a message to me.
3. The sample was prepared yesterday/two days ago / last year - finished action
The sample has been prepared recently / this morning - recently finished action
The sample had been prepared before we arrived.- past action previously finished before another action in the past. "Had been prepared" shows the fact that the sample was prepared before we arrived.
I hope it helps you.
- For Teachers