This might be a dum question but can you play a lantern and a crimson gem or scorpio key.

You can play:

A light object
A heavy object
And any object (heavy, light, or immobile)

Which means you could not play the crimson rock and the Scorpio key together since they are both immobile and you can only play one immobile object.

Also you cannot play 2 of the same special object (exp: 2 yellow lanterns) because they are all unique.

so i can play a blue lantern and the crimson gem correct.

Correct, as it is 1 light and 1 immobile so your third object would have to be a heavy object.

Thanx all for the feedback, i have a team i want to run and wanted to run it with a black lantern, yellow lantern and crimson gem.

You need at least one heavy. You could not have two lights and an immobile.

Damn....wanted gem for attack boost.....

The Gem is an immobile object, so it is fine. You can't have both the Lanterns as they are both light objects.

Or you could play both the Lanterns as long as you play a heavy object with them instead of the Gem.

does this work the same way for golden age 3d objects? where you can play 2 desks and a dumpster?

You cannot play two copies of a single special object, so that's a no on the two desks.

For reference, here's the section from the Player's guide on what types of objects you can use in your force:
 When building a force, players may choose 0-3 objects.
Based on the number of objects a player chooses they can
include:
 1 object – any type (heavy, light, or immobile)
 2 objects – any two types that are not the same
 3 objects – one can be any type, the other two must be
a heavy and a light.