[M4IF Technotes] Object questions

[the_ether]

I have a few questions about arbitrarily shaped objects:
1- What's the maximum number of objects that can exist in a given frame and
does this number vary with the profile?
2- Are there any pointers on how to decide which parts of an image should be
treated as objects and which as part of the background? I suppose factors
could be size of the object, speed of movement and level of contrast between
it and its surroundings.
3- Can I arbitrarily change which objects I am using (ie whereas object 1
was a tree in frame 1, in frame 2 I decide that the tree no longer needs to
be treated as an object and so I allocate object code 1 to a cow instead)?
Or can I only make a change if the new object allocation occurs in an
I-frame?
4- Can objects have holes in them, like a doughnut or are they assumed to be
solid?
5- I noted that I can transmit object information with or without motion
vectors and also with or without prediction errors. What if the shape and
position hasn't changed. Do I transmit anything at all and assume that the
decoder will re-draw what it had last time?
Thanks in advance for any help.
Regards
graham