yes

Perhaps this will help you:
http://www.canoo.net/inflection/freund:N:M

I suggest bookmarking these pages:
http://www.canoo.net/index_en.html
http://dict.tu-chemnitz.de/dings.cgi?lang=en;service=deen
http://en.wikipedia.org/wiki/German_declension
http://coerll.utexas.edu/gg/gr/index.html?si=mis

A LOT of your questions can be answered using those 4 websites (sometimes a combination of two). I use them regularly. By using them I have cut down the amount of questions I ask of Duolingo users by at least half, and I more readily remember what I've learned when I go digging on my own.

Hope that helps! (By all means, keep asking questions though!)

A Gemeinde is more talking about the local social/administrative unit, whereas a "neighbourhood" is more a geographical unit. The English word "community" actually has several more broader meanings - so note that Gemeinde only applies to one specifically.

Gemeinde = "community" or "municipality"
Stadtviertel = "neighbourhood"

Often in Germany you will have several small villages, each a couple of kilometres apart, but collectively considered one Gemeinde.

It's plural. So you may find "In these neighbourhoods I have many friends" could work :)

In German, you have diesen and jenen, but noone really uses jenen ever. So you either say always diesen or you just use a very emphasized den.

Here it is dative, because you talk about a location (where your friends are). If you combine in + accussative, you describe a direction (maybe where your friends are going to: "in diese Gemeinden gehen viele meiner Freunde").

@jholland15: Perhaps 'towns' wouldn't work by itself, but the suggested (aka mouseover) 'townships' would.

because the dependent clause is the first one in the sentence, when that happens the verb in the independent clause moves in the start. This is the subordinate conjunction

There is no single "proper" translation; it depends on whether you are talking about church disticts or the people who belong to a certain church, or about the town you live in. All of them are called Gemeinde.

Yes. The nominative singular is "die Gemeinde", so "den Gemeinden" must be dative plural. Also, in is one of the "two-way" prepositions that can take either accusative or dative. As here it's talking about a "static" state, with no movement or action, that's another pointer to the noun being dative.

So, we the following sentence structure:

[Dative phrase denoting place] - In diesen Gemeinden

[Verb] - habe (in the second position in the sentence)

[Nominative subject] - ich

[Accusative phrase for direct object] - viele Freunde

Where? In diesen Gemeinden! In these communities.

German always puts verbs as the second element in a sentence (for statements at least; commands and many questions put the verb first). So in this sentence the adverbial phrase "in diesen Gemeinden" takes up the first position, so the verb "habe" needs to come right after it. There's no rule that the verb must come before (or after) the subject.

Similarly, we could put the subject first and then "habe" would come right after that: "Ich habe viele Freunde in diesen Gemeinden." Whatever item you put first, the verb needs to come second, right after it.