Can you still play Blu-Ray DVD’s in a regular DVD player?

And can you play regular DVD’s in a Blu-Ray player?

Related posts:

1. Can you play regular DVDs in a Blu-Ray DVD player?
2. Can a blu-ray dvd player play normal DVDs as well as blu-ray dvds?
3. Is it possible to play a regular dvd on a blu-ray dvd player?
4. Will Blu-Ray DVD’s play on a regular old DVD player?
5. BLU RAY – Can you play regular DVD on a Blu Ray player?