2. I thought the difference between an orphan and an invalid block would be that an invalid block doesn't meat the parameters of the consensus. Whereas an orphan is a valid block that is just propagated at the same time with another and it is not sure which one will result in the longer chain. So invalid = fork and orphan =/= fork.
edit: just read your edit and this makes it clear clear for me. Thank you.
an invalid block = blocks that doesnt meet the rules (your understanding of not meeting the parameters)
a rejected block can be valid(data/rule) but for propagation or longer chain or other reasons it just doesnt get accepted.
an orphan is just an umbrella term.
EG real world.
an orphan is a child thrown aside and detached from its parent.
it can be because the parent is killed off.
it can be because the parent no longer wants to be linked to the child (gave up for adoption)
it can be force away from parent (social services removed parental rights)
so in bitcoin the umbrella term orphan, just means thrown aside..
orphans happen alot
http://blockchain.info/orphaned-blocksbut explanations as to WHY, vary. all you can see is what other child replaced it as the preferred child