>>6
>>7
>>8
>>11
these are all correct, but there is one time where "so" and "a" can be used in a different way. when speaking of something that cannot be seen at the current time, and is only known of by the person speaking of said something then so is used. if it is something that both people are aware of then a is used
for example:
two people are sitting at a italian restaurant
person 1 is speaking of a mexican restaurant
person 2 does not know of the mexican restaurant
therefore person one would use そのレストラン(sono resutoran)
if both person 1 and person 2 knew of the restaurant then あのレストラン(ano resutoran) would be used
it is actually more complicated than taught at first. i guess it is just something that you pick up in everyday speach. i have only seen it in one textbook before
oh and the same goes for are/sore and asoko/soko although soko seems to not be used that much in everyday speach