what does "the plantiff hereby incorporates the previous allegiations as if same were set forth fully herein."

Answer 1

In a pleading, each section (or count) needs to be legally sufficient and set forth all the required elements of the claim, as well as all the procedural requirements of the claim.

Often, in a complex case, many of those elements, allegations and assertions will have also been made for other counts or claims.

Rather than inserting that information directly, copy and paste, the document basically says "see above".

If it didn't, and absent copy and paste, then the argument could be made that the claim lacked all required elements and procedural assertions, and thus was vulnerable to attack on those procedural grounds. By saying "see above", the plaintiff avoids that risk.

Answer 2

Plaintiff makes the same allegations, as stated in the previous Cause of Action, for the forthcomming Cause of Action.

(saves the entity drafting the Complaint, from having to repeat the same verbage all over again)

Answer 3

We're making the same charges now that we made before (and potentially some more). Put them into the record without having me go through the trouble of making them again.

Answer 4

Basically - I said it before and I'm not saying it again.
Plaintiff made allegations - and now he still is standing by them, but he is not going to repeat them in a new document.