Answer:
2.I wish I had eaten before going out.
3.I wish I had slept longer, I'm tired.
4.If the order had arrived faster, I would have eaten dinner by now.
5.If I had studied more for the exam I wouldn't have failed it.
Explanation:
2: if he /she had eaten before going out he/she wouldn't be hungry.
3: If she would have slept longer she wouldn't be tired.
4: the dinner didn't arrive fast that is why he/she finished dinner late.
5: he/she didn't finish studying for the exam that's why he /she failed.