About the unlockables, there it seems to be certain criterias for the online icons
You start with 2 icons per character, with their artwork from the select and winning screen
Then, each character has a chibi icon which you unlock if you beat time attack mode with said character, this are not like some guys had in their signs here, for example elisabeth is playing with an Ash doll
Then, if you beat arcade or story mode with an special team, you get their team icon, if you do 5 trials, you get the character icon, and if you play X amount of online matches, you unlock the rest of the icons which are items like terry's hat, jyazu mask, etc
The galleries, finish the game with x team in arcade mode and you will get them all
The invitation seems to be similar
And the colours play 40 matches with each character
About the netcode update, I don't know if it's that easy to just put a patch with this netcode on the other games, maybe snkp don't give a crap for those games anymore, and the cost iwll not be worthy for them, oh well