Im confused about these things in italian?

1) What’s the difference between sciocca and scemo?
sciocca and scemo are the same think, but sciocca, is for female and scemo is for male.

but you can use the same word for a man or for a woman, for example scioccO for a man and scemA for a woman...

sorry for my english is very bad 


2) l'edicola vs. le edicole why does one have apostrophe and the other doesn’t? Shouldn't the plural article+word also have an apostrophe?
because when a word start with a vocal for example APE, you must utilze apostrophe, L'APE. but if i say API the word don't needs apostrophe because is plural
3) Io faccio ginnastica in palestra...

Should this be LA palestra?

4) When someone says "nipote" how do I know if the speaker is referring to a neice/ nephew or a male/female grandchild?

thanks article, infact if you are refer at a man you must use IL nipote, and if you are refer at a woman you must use LA nipote

i hope that you understand my english because is very bad