Hello,
I would advise you to refer to the FlexRay protocol specification.
The questions asked are the very basics of Flexray and as this protocol is not open, you will not have a lot of people using it.
You have both Static and Dynamic slots.
The static slots gives a guarantee of service as the ID has some time RESERVED in the time frame.
On the dynamic part of the frame, the communication works a bit like CAN. Where messages will be transmitted depending on priority. Therefore a Best Effort service.
That is why security critical information can be transmitted on the fixed time frame, so the receiver is CERTAIN when the info is available and for other info, they can go on the dynamic slot.
The slot definition can be different on each A and B channels.
Cheers,
Alban.