If this is included in a PP collection or box set then it is a PP movie and there is nothing one can do to change that PP fact!

the pink panther name sticking to Sellers was accidental. the first movie was a vehicle for David Niven with Sellers as a kind of co-star's co-star. but since the entire movie was stolen by him, The Pink Panther name was attributed to Sellers because it had a nice ring to it: The Pink Panther flows off the tongue. The latter movies except for Return didn't involve the diamond.
The Fearmakers Blog
https://thefearmakers.blogspot.com/

Technically, no, but then I think they often tried to hard to fit the diamond into the plots. Revenge didn't have the diamond either. However, from a formula standpoint it's far closer to the others than the original.
This is where most of Clouseau's more outlandish characteristics were established. Also, the supporting characters debuted here. In a lot of ways, it's the real first movie in the series since the Clousau of the original wasn't the star and was a far more generic character.

It became a Clouseau movie after Edwards came in and reworked it after production started.
Correct.
"It's the system, Lara. People will be different after the Revolution."

If that's your opinion far be it to convince you otherwise. It also has Cato, Dreyfuss, and other trademarks. Literally, it is not a PP movie. Would it be right to exclude it from the collection however? It would be a shame for someone not to see it because it was not identical to the others. It became a Clouseau movie after Edwards came in and reworked it after production started.