Der Bus fährt in zehn Minuten vom Bahnhof ab.

Because the full verb is abfahren = to depart / to leave.

In a normal main clause, German separable verbs split:

• the conjugated part goes to the usual verb position
• the prefix goes to the end

So:

• abfahren → Der Bus fährt ... ab.

You can see the full verb stay together in places like:

• infinitive: Der Bus wird bald abfahren.
• subordinate clause: ..., weil der Bus bald abfährt.
  (Here it is still written as one word because it is a finite form.)

So in your sentence, fährt ... ab is just the split form of abfahren.

Because the subject is der Bus, which is third person singular: the bus.

The verb fahren changes like this:

• ich fahre
• du fährst
• er/sie/es fährt

So:

• Der Bus fährt ...

Also, fahren is a strong verb, so the vowel changes from a to ä in some present-tense forms.

vom is a contraction of von dem.

So:

• vom Bahnhof = von dem Bahnhof

This happens because von takes the dative case, and Bahnhof is masculine:

• nominative: der Bahnhof
• dative: dem Bahnhof

So:

• von dem Bahnhof
• usually contracted to vom Bahnhof

This contraction is very common and sounds natural in everyday German.

Because von is a preposition that requires the dative case.

So the article changes:

• der Bahnhof → dem Bahnhof

That gives:

• von dem Bahnhof
• contracted: vom Bahnhof

This is something you simply learn with the preposition:

• von + dative

Because von and aus are not used in exactly the same way.

• von = from a place / from a point of departure
• aus = out of the inside of something

With transport, vom Bahnhof usually means the bus departs from the station area / station stop / station as a location.

aus dem Bahnhof would sound more like the bus is coming out of the inside of the station building, which is usually not the intended idea.

So vom Bahnhof abfahren is the natural expression for departing from a station.

Here it means ten minutes from now.

So the idea is:

• The bus leaves in ten minutes.

This is different from:

• für zehn Minuten = for ten minutes
• zehn Minuten lang = for ten minutes / for a duration of ten minutes

So:

• in zehn Minuten = after a period of ten minutes
• für zehn Minuten = for a length of time

Here in is being used in a temporal sense, and it takes the dative.

With zehn Minuten, you do not see much difference because:

• it is plural
• the noun already ends in -n

So the form does not look very different.

You can see the dative more clearly in examples like:

• in einer Stunde = in an hour
• in einem Monat = in a month

So in your sentence, in zehn Minuten is a time expression meaning in ten minutes.

Yes, it could be different. German word order is flexible, but there are patterns.

In a main clause, the conjugated verb usually stays in second position:

• Der Bus fährt ... ab.

After that, German often prefers something like:

• time before place

So:

• Der Bus fährt in zehn Minuten vom Bahnhof ab.

That is a very normal order.

You can also move parts of the sentence for emphasis:

• In zehn Minuten fährt der Bus vom Bahnhof ab.

That puts extra focus on the time.

So the sentence order is natural, but not the only possible one.

Because German usually uses an article with singular countable nouns in normal sentences.

So:

• Der Bus fährt ...

is the standard way to say it.

English sometimes drops the article in certain styles, like headlines or timetable language, but German usually keeps it in ordinary sentences.

Because all nouns are capitalized in German.

So:

• der Bus
• der Bahnhof
• die Minuten

This is one of the most noticeable spelling rules in German.

Yes. That would still be a correct sentence.

• Der Bus fährt in zehn Minuten ab. = The bus leaves in ten minutes.

Adding vom Bahnhof simply gives extra information about where it is departing from.

So:

• without vom Bahnhof = the place is not mentioned
• with vom Bahnhof = the departure location is included

It is very common for means of transport such as:

• Busse
• Züge
• Straßenbahnen
• Schiffe

Examples:

• Der Zug fährt um 8 Uhr ab.
• Die Straßenbahn fährt gleich ab.

It can also be used more generally for departing, but with public transport it is especially common and natural.