"Мойбратиграетвфутбольнойкоманде."

You are wrong. "Soccer" is also used in Australia (where "football" means Aussie Rules), and in New Zealand and Japan. "Football" in Australia and NZ also means Rugby League. I am English and I remember that I and everyone else used to call the game "soccer" up until sometime in the eighties. It's a good old English word, invented by members of Football Association themselves in the 1890s. It is, of course, short for "Assoc. Football," which is what they used to print on the posters advertising upcoming matches. For reasons known only to themselves, British football fans saw fit to deprive themselves of their own nickname for the sport, just because the Americans ONLY used "soccer" and refused, quite rightly, to call it "football" since they already had a sport called that, thank you very much! This action by British soccer fans is what we used to call "cutting your nose off to spite your face."

In Quebec, we say ''soccer'' too.

"As far as I know, the US is the only country in the world that says soccer " Not that it is normal for all, but on both British and Australian shows, they do say Soccer from time to time. I believe I have also seen a show in New Zealand where they called it soccer as well.

In portuguese we also call it 'american football"

The word "soccer" is a bit offensive, specially when you are from Argentina.

"As far as I know"! Yes, well, you don't know very much, do you? "Soccer" is also used in Australia, New Zealand, and Japan, among others. It is also used by me, and I am English. We ALL used "soccer" (a word invented by Englishmen in the 1890s - short for "Association" - and used by ALL classes of people) to refer to Association Football up until the 1980s or thereabouts, or had you forgotten? And some of us still do.

No full-form adjective looks like that (check the endings ). Basically, all Russian adjectival endings are at least two letters long and always start with a vowel.

The major exception is how "animal-possessives" and the word for "third" behave. They have a /j/-sound after a soft consonant almost everywhere in their endings: третий→третья,третье, третьи, третьего, третью... Normal adjectives have two vowels instead of ь + vowel and just -его, -им instead of -ьего, -ьим.

Anyway... to have a neuter SHORT-form adjective as a predicate here, you would have to actually have the predicate consist of "to be" with an adjective. In reality, "plays" is the verb that acts as a predicate in the sentence.

Therefore it makes no difference whether you use "in", "on" or "for".

"For" only implies that you're playing something (could be soccer, but not necessarily) to the benefit of the soccer team, whereas "on" would not leave any doubt about the fact you are indeed one of the team's participating players.

It's a regular adjective with a regular adjectival ending. Lots of nouns in Russian become adjectives by adding -ский, -ний, etc. The adjective is in prepositional case with a feminine ending to match the case and gender of the noun (команда) it is describing.

Looking at the Russian Euro 2016 website, I got the impression that
команда = team &
Состав = squad.

Could any native Russian speakers confirm this please?

Well, "My brother plays soccer in a team" in English sounds like there's a version of soccer where people play solo. The Russian for that would be something like "Мой брат играет в футбол с командой" which would express that he plays with a team in soccer as opposed to by himself, but it looks strange to me in both languages.

why "is"? if he is playing just now so ...is playing... otherwise ...brother plays....

Because adjectives, just like nouns, also decline based on gender, number and case. futbolnaya (футбольная) is the feminine [gender], singular [number] nominative [case] version of the adjective, but in prepositional case (and dative and genitive cases), the feminine singular ending of adjectives is -ой/-ей.

You know nothing. How old are you? I'm 67 and I remember myself and EVERYONE else in England calling the game "soccer" (as well as "football" of course) in the 1950s and 1960s. The word "soccer" (short for Assoc., as in Association Football - the sports's official name) is a good old English word invented by top officials of the Football Association in the 1890s, soon after the sport got going. It was used by ALL classes of English people until sometime in the 1980s, when the football-fan morons of England decided that they were going to cut off their noses to spite their faces! They stopped using THEIR OWN WORD just because the Americans (quite rightly) ONLY called it "soccer," and refused to use "football" because they already had a sport called that. I'll remind you that rugby is officially "Rugby Football," and that there is also Gaelic Football and Australian Rules Football, all of which - being equally descendants of the old county footballing codes along with American Football - have equal right to use the name "football." "Soccer" is used not only in the USA, but also in Australia, New Zealand, Japan and several other countries.