Is there another way 2 redo the hollowen level?

Sadly, no. That's why your savefile's called Endless Summer.

Yes, Endless Summer mean ENDLESS. Can't go back.
BUT! I hear about Endless Halloween Glitch.
If you wanna knows:
-Go back to Chapter I[use new save file]
-When Halloween, "busted" by prefect at 01:30-02:00[to spawn a prefect, attack girls or kids]
-You'll awake at Principal Office,but everyone still in their costume, and if you did'nt complete Big Prank, there's no prefect around so enjoy!

NOTE: To continue the glitch,repeat Step 2

Source:Wikia Games

This is my trick if you want to play the halloween again save it in an another file but dont save anything else when you save your halloween there

NEVER.Fail the Big Prank or sleep and you never can beat it.

Just copy your ssave file and load it from there

Actually, no. But there's a glitch that can make Endless Halloween as well. To do that, during Halloween, get busted between 1:30am and 2:00am. If done correctly, you will be awake past 2:00am. The students will still be wearing their costumes and you still can play those missions. You will have to get busted between those times everyday to have an Endless Halloween glitch. Hope that helped.