a quick question, do you know a workaround to restore data into unity 5.0 from a unity 4.X ?
You mean from a DiRT backup? No, there's no work around here - you'll have to restore to the 4.x version that was backed up and then upgrade. DiRT does table based restores and full branches of the registry - if new tables are added or structures are changed and/or branches in the registry are moved/added etc... the resulting system is unusable. There's simply no way to work around that.
If you're not talking about DiRT but something else, please let us know.
For moving users/call handlers and such you can use COBRAS to go from 4.0(5) to 50 (you can't go any earlier than 4.0(5)) - it doesn't get as much data as DiRT but it may be enough for your purposes if installing and upgrading is not doable.
More information about COBRAS can be found on its home page (help and training videos):