Riddles - 2

Riddle - 1:

Does a pound of gold or a pound of feathers weight more?

Riddle - 2:

Find a 10-digit number where the first digit is how many zeros in the number, the second digit is how many 1s in the number etc. until the tenth digit which is how many 9s in the number.

Riddle - 3:

Spaghetti is famous for the way it all gets tangled up on the plate. Those of you who think they know their alphabet are bound to get all tangled up with this puzzle too, unless you read it and think about it very carefully!

What letter of the alphabet is the one which comes eight letters before the letter which comes five letters after the fourth appearance of the first letter to occur four times in this sentence?

Riddle - 4:

If I said that in three days' time it would be a Thursday, I am sure that most of you would have no difficulty telling me that today was a Monday. 

Try this one then. Yesterday was two days before Monday. What day is it today? Yes, you're right again. It's Sunday. Do you get the idea? 

Now let's tackle a similar question from The National Mathematics Contest (1991) Paper:

Three days ago, yesterday was the day before Sunday. What day will it be tomorrow?