My experience with old, factory-sealed powder developer is: if it’s still white, or nearly so, it’s likely still good.
Be aware that developer tends to rapidly absorb the water content of room air once you’ve opened the sealed container. That will begin degrading the developer. To prevent this, BEFORE opening the package, have enough canning jars with good seals on the lids ready to accept the powder as soon as the package is opened, and the contents examined.
If you’re satisfied with the color, immediately separate the developer among as many jars as needed and seal the lids tightly. Use a funnel to transfer the powder into the jars so that none of the crystals get onto the lip of the jar, as such particles could compromise the seal.
I recommend not bothering with weighing at this time, as you want to get the developer into the jars and sealed quickly to minimize the absorption of water vapor from the room air.