«Мои» (note the stress: мои́) is a plural form (вот мои́ о́фисы — here're my offices), «мой» is singular masculine form (вот мой о́фис — here's my office).
There's also a singular feminine form моя (вот моя́ ко́мната — here's my room) and singular neutral form моё (вот моё зда́ние — here's my building). To find out the gender of the singular noun, you can use a dictionary (later you'll learn to guess it from the form of the word). The plural nouns don't have a gender.
Er... Not sure. Maybe if they are really really really really lazy, but then why type at all?
Каждый день подарки по фильтру-Рад обмену-Пожалуйста добавляйтесь только активные игроки от 5 уровня-Уважайте мои просьбы остальных все ровно удалю можете даже не добавлятся- 54 Уровень
Ищу друзей которые будут дарить БП ежеденевно. Больше от вас ничего не прошу и не требую и не выпрашиваю.
Тока сегодня увидела, что есть ангар подземный. Не акция, даж и не чухнула бы
This post is an example of very sloppily written messages that nevertheless have the и/й distinction.
Those messages are about some game and it's difficult to translate then without knowing the context. Ангар подземный is really 'underground hangar/airshed'.
The rough meaning of the messages is:
Gifts every day according to a filter — [I] would be glad to exchange — Please join only if you're an active player, level 5 or higher — Respect my requests, if you don't I'll delete you anyway, so just don't join — 54 level
I'm looking for friends that will give me a gift of БП [???] every day. I don't ask you to do anything else, I don't request or beg for anything else.
I've just seen it today that there is an underground hangar. It's not a [temporary] event; I wouldn't even have noticed it.
no, it's diffrent letters and sounds and we never replace it by each other и is a vowel and sounds like "i" in "fish" й is a consonant and sounbs like [ɪ] in "pie" and "toy"
the situation that you describe is suitable for е and ё russians often write ё like е even in handwritten texts, but it's still read as [йо] so this can create difficulties if you don't know that "e" is actually "ё" in the specific case for example мы передохнём - we'll take a rest мы передóхнем it's pejorative, correct - мы умрём) - we will die