Can it be that the propeller blades & Srews for Mini 3 Pro and Mini 3 are different ?

I have seen that the small screws for Mini 3 Pro are different than those for Mini 3

As for the propeller blades I do not know if these are also different ...

Have a look at these photo to see the reason for the differing screws.

mini 3 pro =

mini 3 = also mini 3   
the actual propeller blades are the same.

Have a look at these photo to see the reason for the differing screws

I assume the photo shows the motor from a Mini 3 Pro and has these two metal threaded towers
around which the propellers rotate and the Mini 3 does not have these two towers but only a short
thread on the surface of the motor housing and the propeller rotation takes place at the screw, right ?

Correct.

Hi there. Thank you for reaching out. Both propellers of the DJI Mini 3 Pro and DJI Mini 3 are the same however, the provided screws are different therefore, they are not cross-compatible. Should you have other inquiries, please don't hesitate to reach us. Thank you.

Carefully add a little threadlock onto the old screws. I have done this many times without any problems

Gordon Graham2 Posted at 8-26 04:38
Carefully add a little threadlock onto the old screws. I have done this many times without any problems

But be careful to use the right threadlock, you’ll find it hard to removed the ‘permanent type’.