OK, I'm trying to decide between a bunch of Nokia GSM phones for
people.  We want to use common headphone adapters, common car
chargers, common add-on programs.  The problem is that there seems to
be almost no reason to Nokia's numbering schemes as it relates to
these attributes.  To be more precise, the things we're interested in
at the end of the day are:

1. Connnector type(s) on the bottom of the phone (affects headset choices)
2. Operating System (e.g. basic phone, Symbian series 60, Symbian
series 80, etc) And, are all the non-symbian phone OSes the same? 
It's so confusing.
3. Auto answer.  This one is critical to us for working in a lab
environment.  Some Nokia's have an auto answer feature when a headset
or car adapter is plugged in.  Some don't.  Nokia's own website is
inconsistent at listing this capability.

Soooo, the question(s)

A. What is the basis for the Nokia numbering Scheme? I've put what
I've found by web searching below, but it's incomplete.  I want to
know what the first number, second, third, and fourth numbers relate
to and how to decode.

B. What are the operating systems on these phones (if the numbering
scheme doesn't answer that already)

C. What is the port type on these phones (if the numbering scheme
doesn't answer that already)

D. Bonus question: Answer this one, and I'll throw in an extra $20.  I
realize this may be a tough one to do. [If I'm not allowed to price
the question that way, let me know and I'll break it out as a separate
question.] What are the phones that do (and do not) have auto-answer
feature, which means, usually when a headset is plugged in, that the
phone automatically picks up after a certain number of rings with no
user intervention.  I am NOT interested in getting yet more links to
those stupid spy-phone programs you can add to various phones. 
Legitimate auto answer systems only.

--------------------------------
Here's what I've found so far on the web:

1XXX and 2XXX - Basic Category phones (mainly voice-centric,
entry-level phones mostly for prepaid and emerging markets)
3XXX - Expression Category phones - generally relatively low-cost
phones, but with youth-oriented features like changeable covers,
downloadable ring tones, etc.
5XXX - Active Category phones - rugged phones designed for a more active user 
6XXX - Classic Category phones - full featured, conservatively styled
phones - mainly for mid-line business-type users
7XXX - Fashion Category phones - higher price, small phones with
unique, flashy designs
8XXX - Premium Category phones - highest price, more conservative
style, but high-end materials and finishes
9XXX - Communicator Category phones - converged, keyboard enabled devices 

xx90 -- world phone: GSM + North American GSM, e.g. 8890
xx30 -- GSM except North American -- EGSM900/EGSM1800, e.g. 3330
xx50 -- GSM except North American -- EGSM900/EGSM1800, e.g. 8850
xx65 -- North American phones, AMPS/TDMA800/TDMA1900 ATT Network, e.g. 6165
xx85 -- North American phones, AMPS/TDMA800/TDMA1900 ?? Verizon network

Phones that allegedly have auto answer with a plugged in headset/car set:

2600
3310
3330
3350
6150
and what else?????