Yes, there are dual portable cassette players.
Yes, there are portable cassette players with digital displays. Check online for the biggest selection.
Yes there are portable CD players that also play cassettes, but are only found in boombox styles.
no - I did not find any water proof cd players
Anyone can buy portable DVD players online, it is not hard to find and also cheap to buy. You will find a huge range of quality portable DVD players at a cheap price on Amazon almost any day.
You will need to purchase full sized headphones seperatley,portable CD players come with mini headphones.
I am sorry there are no portable CD players that hold more than 6 disc available.
Yes, any standard set of headphones should plug into a portable cassette player.
Some portable cassette players are waterproof. The fully submersible Swimman works to ten feet and operates on 2 AA batteries.
Yes, most sony portable DVD players have USB input jacks. You can find however, many different types and styles of portable DVD players, so be sure to check the specific model that you want to buy.
no - not since ipod came out
Yes there are many portable mini disc player products that light up.