Ok, there's a couple of things wrong with this. #1: How Dante became silent, mature, and serious into a goofball as her once was? The story didn't even explained why he's changed (so does DMC2) nor didn't explained why he leave things to date by tossing a coin.
#2: His Majin Form wasn't even in DMC4 which doesn't make any sense.
#1 dmc 2 is simply bad written and I say this million of times, there was another director and different team that made this game it wasn't the same from dmc 1 and they decide that it would be cool to have dante silent, but they were wrong, there is no actually story reason for that it simply a stupid choice made by developer who weren't able to write a good story (I write this million of times in this thread and also in the one post you quoted)
#2 Majin form his a desperate dt form and he used it in dmc 3 manga and dmc 2 gameplay, it s like a non perfect sin devil trigger, dante has no need to use it in any situation because he is never in danger, chronologically happeared first in dmc 3 manga, you can say why didn t he use it in dmc 5 prologue, or dmc 3 or in dmc 1 against mundus ? Well that would be a good question...
Dmc 2 story is so poor bad written and stupid that they could have put it before dmc 1 or after it, or after 4 or after 5, the story is not connected to any game so you can put him everywhere, and really who care about that game, I like it but it's a bad bad bad Game, itsuno worked hard to forget that game, who was one of the worst game ever made, and finally give us 3 fantastic dmc game, 3 4 and 5, so who really care about 2, Capcom made the mistake to give dmc 2 to another developer team but this team was unable to make a good game or write a good story, Infact it's only inconsistence whit the rest of the series, we must only thank itsuno who take dmc 2 in the last 5 month of development, Infact the only good thing about that game are probably made by him, like rebellion who he used it again in dmc 3 and some of the move that will be used for dmc 3 style...