So which old content i can do unsync?

[MistakeNot]

That's exactly the reason you can't do Ultimates unsyncked.

^ This.
Challenge is the sole and entire reason the ultimate raids even exist. A central part of the design of the Ultimates is that they are very tightly synced, making it impossible to outgear them.
You don't have to like that, but then you don't have to do Ultimates either.