KRviator, it's possible to provide FF without assigning a discrete code - "squawk ident" and manually attaching a RADTAG (an ad hoc label that has no associated flight plan) to the relevant SSR return. Usual practice would be to assign the SSR code associated with the RADTAG but it could get forgotten about (as we're seeing a label with your callsign regardless) or the service is terminated before the code is assigned (assigning you a code isn't high on the list of priorities).
A lot of VFR flight plans never make it into TAAATS, the exception being if your tracking and level will mean you potentially require a clearance, so pre-filing is no guarantee we'll know anything about you.
MagnumPI, with respect to requesting a continuation of FF into another sector, I think that needs to be read in conjunction with the previous paragraph where the controller is terminating FF. Normal practice would be to hand you over to the next sector after coordinating your details and gaining their agreement to accept you. The only time I'd usually cancel FF at the boundary is where I expect you to leave radar coverage shortly.
As far as preventing you entering CTA without a clearance we'll do our best, but you have to help by telling us whenever you want to change level or tracking because if we're using a RADTAG we don't get all the alerts for deviations from levels or tracking. You could merrily climb into CTA unannounced and unless we happened to notice at the time we wouldn't stop you, arrange a clearance or provide traffic.