Learn Italian: Mangio molta frutta: per esempio, mele e arance. - I eat a lot of fruit: for example, apples and oranges.

It would change the meaning! Cioè and ossia mean "that is" or "namely." If you say Mangio molta frutta: cioè mele e arance, you are implying that apples and oranges are the only fruits you eat. Per esempio ("for example") shows they are just part of a broader list.

Why is it molta frutta instead of molto frutta?

Here, molto is acting as an adjective describing the noun frutta, so it has to agree with its gender and number. Since frutta is feminine singular, it becomes molta. If it were an adverb modifying the verb (like mangio molto, "I eat a lot"), it would stay masculine singular.

Why use the singular frutta when talking about multiple types of fruit?

In Italian, la frutta is a feminine singular collective noun used to talk about fruit in general, especially as food. There is a plural word, i frutti, but that usually refers to the specific products of a plant (like the fruits of an apple tree) or metaphorical results (like the fruits of your labor).

Why is the plural of arancia spelled arance without an "i"?