Can I use 行きます instead of 帰ります (hope I used the right kanji) to say "I go home..."? Latter sounds like "I return home..."
In Japanese, you always say "return home" 帰る to mean "go home".
Why can't i just use "午後六時いえにかえります"? Is the first に necessary?
に is necessary for specific dates and times, like "on monday", "in february", or "at 11 o'clock".
In this case you have one to indicate the time, and one to indicate the direction. Two seperate functions, both need a に.
Is the first に really necessary, and why?
What is the difference between ha, ta, wo, ni, and any other words like that?
It's too long for a reply but you should study Japanese particles.
「いえにかえります」 feels redundant. Is it not?