Can a druid take a wild shape form then shape into another for an keep the abilities from the first form? For example A moon Druid shapes into a Fiendish Giant Spider. resistance to cold. fire, and lightning damage, and immunity to poison damage. They are also immune to the poisoned condition.

Now the part of the players handbook comes into play: Vou retain the benefit of any features from your class, race, or other source and can use them if the new form is physically capable of doing so.

Then from that form as a bonus action in the same round shift to a cranium rat. Keeping the resistance and immunities. On that note since it's a poison bite and not a venomous bite even keeping the added save per bite.

To clarify this question is about Other Sources variation.

Using up the 2nd shift. Could you make a hybrid form? Much like later when as a moon druid you can make an Elemental form with 2 uses of wild shape.