Assuming you aren't using DFHack:
1) No
2) No
3) Squad members are culled in worldgen.
4) You can use [ALLOWED_CREATURE:<creature>:<caste>] for positions, and for professions, you cannot stop specific castes from working, but you can make sure they never get good at it with [SKILL_RATE:<skill>:NONE:1:1:1].
5) As above, you can use [ALLOWED_CREATURE:<creature>:<caste>] to allow only the entity's creature to become a position holder in that entity; but you cannot stop immigrants from accepting any profession.
6) Law-givers appear when you have [VARIABLE_POSITIONS:LAW_MAKING] enabled.
7) No you can't, but you can discourage some labors (see answer 4).
8
) No, and there's nothing more to that.
9) Use [SUCCESSION:BY_POSITION:<position1>] in position2 to make replacements for position2 be picked from people currently in position1.
10) I believe not, although you can have the monarch draw from counts and the count draw from barons.
11) No
12) Masterwork DF has lots of pseudo-real-life languages, you can find them in language_all.txt.
13) No
14) Impossible
15) You can have thousands.
16) You can make the plant production process a custom reaction, then use [PERMITTED_REACTION:<name>] in only one of the entities.
17)
http://www.bay12forums.com/smf/index.php?topic=118085.018) You won't reach the limit
19) No
20) Yes, you can select the technologies they are able to use with [PERMITTED_JOB:] and [PERMITTED_REACTION:].