Yeah, my router messed up a while ago because the electricity wasn't paid, then one of my father's friends got it to work.

And then when I finally got to play the DLC because apparently, you can't play DLC offline, yeah so I played mercenaries reunion and all of my scores were gone, the best ones were still on leaderboards, but nowhere to be found when I hosted a game.

And before that, the game said I got all the characters and costumes in Mercenaries reunion and single player, why did that happen?

Can't play DLC offline? My connection was messed up for a long time and it still played well Couldn't play online of course.

That doesn't make sense. You don't need an internet connection to play DLC. You only need it to play DLC online. Did the power in your home go out because the electricity wasn't paid? If so, was the PS3 on at the time? If so, that is your problem. Probably messed up the harddrive or something.

it had to be an ownership error on your sydtem, which set Playerowns=1
to playerowns=-1
That made it an overdue 'trial' and blocked it.
Your Ps3 also might've thought the scores were unnecessary and purged them

My ps3 did the same with my HDMI settings

360 does the same thing, its a calendar error.