*Is not the maker of this RP*

You are allowed more than one character, yes-Siesses did that.

There are crestless characters, and they do seem to be capable of evolving their Digimon without assistance-all the way to Mega, even. Only the crested score Bio-Merging (apparently), and a Bio-Merge has a few benefits-otherwise, though, Mega requires some special circumstances from what I gather. Otherwise, unless you're explicitly limiting yourself, having a Crestless that goes all the way to Mega is possible. I'm not an expert on Digimon in any sense (indeed, my character is me using this problem of mine as a character trait and didn't start with a Digimon), but DNA Digivolution is definitely possible and one of the ways a Crestless can hit Mega from what I gather. I don't know about all those other terms, though...

Not sure on length, though, but I'd say it's in the middle.