What specific sizes, pressures, temperatures and fluid spec's are the gaskets rated for?

Many times, they can be substituted for one another. Other times, they cannot be substituted.

The project where I am working at has not started the construction stage yet. Right now they just started receiving materials to prepare for next year. It is my second week at this site and they have not provided me with the specs. At this time I dont have the information where the material will be allocated to. The gaskets are dn 50 pn 10/40, flanges are 2" 150#
I will appreciate any information

Same answer applies.

UNTIL you KNOW the service conditions (pressure, fluid properties, temperature, and ratings of the pipe and flanges), you CANNOT specify nor purchase the gaskets that will
(1) fit between the gasket faces of the flanges
and (2) protect the fluid and your customer from the pressurized fluids/gasses/steam/HP air inside the pipe..

You're trying to make wrong spec'ed gaskets (metric/DN to ANSI/inches) "fit" the hole around the pipe.
That's the wrong question. And the wrong answer will kill people in future. Maybe. Or maybe not.
Maybe these gaskets are way too strong, too thick, and too expensive. Maybe they'll melt through in 10 minutes. Or maybe not.

You don't know yet.

Thank you racookpe.