What is the difference between the CBSE Delhi papers, All India papers, and Foreign papers? How is the difficulty level for each? Are the questions different? Is foreign more tougher?

Basically CBSE sets out different question papers for different regions.

There is a rumour that the Delhi set is harder whereas Foreign is easier but as I have come across the previous 5 year question papers from Delhi and foreign set. I’ve felt that all are of similar difficulty with a few different questions which arise every new year as usual.