I have one from some one from this site, the story is "Accidental Multiverse Planeswalker" it has a mature content if that bothers you. The chapter are long and the story is quite intriguing. It also has the same concept as you in the multi-vers part but it takes a different road in the way it is handled. 

It has 20 something chapter but almost all of them are over 20 -30 thousand words and more. The author right now only works on it occasionally but I recommend giving a read to the three first chapters and seeing if you find inspiration in the writing. 

50.000 word per chapter damn... 

Yea anything Bokuboy writes are mostly awesome 😎👍 Check out his stuff.

i don't know who that is, i barely know of half the fandoms (speaking of, what are the chances of undertale getting in the chat?)

even then, swapping the gender of one character is debatable at best, especially if the cannon of the story is, 'in this fanfiction, they have always been that gender', that is closer to an Ooc then anything else (i am trying to not sound rude, this is my 5th attempt of typing this, the others sounded too rude)

Valiana Lucifer From DxD? or from some other place

Yes from DxD