Italian: grammar

When does the singular and plural form of a noun stay the same (doesn't change in either singular of plural form)

How do feminine nouns ending in -ca and -ga end in plural?

What is the plural of Amica?

What is the plural of "riga" in plural?

In what cases does the nouns ending in -cia and -gia take -ce and -ge in their plural form?

What is the plural of "zio" in Italian?

What is appetizer in Italian?

What is "pasta course" in Italian?

What is "meat course" in Italian?

What is "side dish" in Italian?