Στο άλλο πιάτο έχει σπανάκι, λάχανο και λίγο καλαμπόκι, και φαίνεται πολύ καλό.

Literally, Στο άλλο πιάτο means in/on the other plate.

• στο = σε + το
• σε is a very common preposition that can mean in, at, on, to, depending on context
• το is the neuter singular definite article the

So:

• σε το άλλο πιάτο → στο άλλο πιάτο

Greek often uses σε where English might choose either in or on. With plates, English usually says on the plate, but Greek commonly says στο πιάτο.

Because πιάτο is a neuter singular noun.

The adjective άλλος (other) has to agree with the noun in gender, number, and case:

• άλλος = masculine
• άλλη = feminine
• άλλο = neuter

Since πιάτο is neuter singular, Greek uses άλλο:

• το άλλο πιάτο = the other plate

Yes. After σε, Greek normally uses the accusative.

Here the noun is:

• nominative: το πιάτο
• accusative: το πιάτο

For this noun, nominative and accusative look the same, so you do not see a change in the noun itself. But grammatically, after σε, it is accusative.

So:

• σε το άλλο πιάτο / στο άλλο πιάτο

This is a very common colloquial Greek use of έχει.

Normally:

• έχω = I have
• έχει = he/she/it has

But in everyday Greek, έχει is also often used impersonally to mean:

• there is
• there are

So here:

• Στο άλλο πιάτο έχει σπανάκι...
  = On the other plate there is/there are spinach...

This is very natural spoken Greek. A more formal or textbook-style alternative might use υπάρχει / υπάρχουν, but έχει is extremely common.

Because this use of έχει is impersonal and fixed in colloquial Greek.

Even though the sentence mentions several items:

• σπανάκι
• λάχανο
• λίγο καλαμπόκι

Greek still very naturally says έχει.

It works a bit like saying:

• There’s spinach, cabbage, and some corn on the other plate

Even in English, there’s is often used informally before a list. Greek does something similar here.

Because they are being used as indefinite food items / mass nouns.

In this sentence, the speaker is just listing what is on the plate:

• σπανάκι = spinach
• λάχανο = cabbage
• καλαμπόκι = corn

This is similar to English, where you would also normally say:

• There is spinach, cabbage, and some corn

  not:

• There is the spinach, the cabbage, and the corn

Greek often leaves out the article when naming foods or ingredients in this kind of context.

Because καλαμπόκι is neuter singular, and λίγος / λίγη / λίγο must agree with it.

Forms of λίγος (little / a little / few, depending on context):

• λίγος = masculine
• λίγη = feminine
• λίγο = neuter

Since καλαμπόκι is neuter:

• λίγο καλαμπόκι = a little corn

Also, καλαμπόκι here is treated as an uncountable food item, so λίγο means a little rather than few.

Yes, σπανάκι is singular, and that is normal.

In Greek, many food words are treated as singular mass nouns, just as in English:

• spinach
• cabbage
• corn

So:

• σπανάκι = spinach
• λάχανο = cabbage
• καλαμπόκι = corn

Even though these can refer to many leaves or kernels in real life, grammatically they are often treated as singular food substances.

φαίνεται πολύ καλό means it looks very good.

• φαίνεται = it appears / it looks
• πολύ = very
• καλό = good (neuter singular)

The adjective καλό is neuter singular because it most naturally refers back to something neuter, probably:

• το άλλο πιάτο = the other plate / dish

So the idea is:

• The other plate looks very good
• or more naturally in English: It looks very good

In food contexts, Greek may use the neuter like this to refer to the dish as a whole.

Because καλό is an adjective, while καλά would usually be an adverb or plural/neuter plural form.

Here the sentence is describing it:

• φαίνεται πολύ καλό = it looks very good

So καλό agrees with the thing being described, which is understood as neuter singular.

Compare:

• Είναι καλό. = It is good.
• Πηγαίνει καλά. = It is going well.

In your sentence, the meaning is descriptive, so the adjective καλό is correct.

The first και joins items in the list:

• σπανάκι, λάχανο και λίγο καλαμπόκι
  = spinach, cabbage, and a little corn

The second και joins two clauses:

• Στο άλλο πιάτο έχει...
• φαίνεται πολύ καλό

So it means:

• On the other plate there is spinach, cabbage, and a little corn, and it looks very good.

Greek uses και just like English and in both of these roles.

It can mean both, depending on context.

• πιάτο can mean the physical plate
• it can also mean a dish/serving of food

In this sentence, Στο άλλο πιάτο most literally means On the other plate, but in natural English you might also understand it as On the other dish / in the other serving depending on the situation.

This is one reason why φαίνεται πολύ καλό can feel like it refers to the food as a whole.

Yes, it sounds very natural.

Especially natural features include:

• στο instead of σε το
• using έχει to mean there is/there are
• listing foods without articles
• ending with και φαίνεται πολύ καλό

A slightly more formal version might use υπάρχουν or structure things differently, but the sentence you have is perfectly normal everyday Greek.