I played the survival stage like 90 minutes with LightningFreeze today.
Me with Firen and lf with Freeze at difficult :P
The highest stage we got was Survival Stage 10 ... we loose against Julian there :/
sorry i didn't made a screenshot or record-file ^^''
It's not SO hard to reach level 20. It's the way how you play.
It's much easier if you use 5000 DragonPunches and drink all bottles like marti ^^ (he reached level 20, too)