Lol
All of Hashirama's jutsu are absorbed. The Mokuton argument doesn't work since Naruto was about to use Shadow Clones yet Sasuke told him not to because it'd be absorbed. Not to mention he can even absorb Shikamaru's shadows. So he wins. And if his basic attacks can damage Mini PS Kurama then his stronger ones should do some damage to SS.
Hashirama only has a chance in S1 since Momoshiki is left with nothing but Taijutsu and chakra receivers. He might actually win since Momoshiki's combat feats in Base are pretty much nonexistant. He can hang with Darui and Gaara at once but then again Hashirama would easily do the same himself, especially with Sage Mode. He didn't fight Adult Sasuke in CQC so no one bother bringing that up.
The OP stipulates that this is Demon Momoshiki in both scenarios. The first scenario starts with him not having any pre-absorbed
jutsu so he only has taijutsu, but he still is in Demon form, which was capable of going toe-to-toe in CQC with Naruto and Sasuke.
Hashirama in SM or not is not beating that in CQC. Also, when a jutsu gets absorbed, the whole thing stops working. It's not like
if you launch a giant fireball, only the part being absorbed gets absorbed while the remainders continue on and fry Momoshiki.
Nope. The whole thing loses all effect. So the thousand arms thing doesn't work.
And my gosh.... just imagine what Momoshiki can throw back after absorbing that. Seeing how much the jutsu gets scaled up,
it might be just as great as Madara's IT absorption mokuton level.
