После работы я зайду в аптеку и заодно куплю хлеб; изредка я так и делаю по дороге домой.

Because после requires the genitive case.

• работа = nominative
• работы = genitive singular

So:

• после работы = after work
• literally: after (of) work

This is a very common pattern:

• после урока = after the lesson
• после фильма = after the film
• после обеда = after lunch

Зайду is the 1st person singular future of зайти, a perfective verb.

Here it means:

• I’ll stop by
• I’ll go in
• I’ll drop in

So я зайду в аптеку is not just I will go to the pharmacy in a neutral sense. It suggests a brief visit or a stop along the way.

Compare:

• я пойду в аптеку = I’ll go to the pharmacy
• я зайду в аптеку = I’ll stop by the pharmacy

This is a very natural choice if the speaker is mentioning a quick errand.

Because the sentence expresses motion toward a place, so в takes the accusative:

• в аптеку = into / to the pharmacy

If it meant location, it would use the prepositional:

• в аптеке = in the pharmacy

So:

• зайду в аптеку = I’ll go into the pharmacy / stop by the pharmacy
• я в аптеке = I’m in the pharmacy

This is one of the most important Russian patterns:

• куда? where to? → accusative
• где? where? → prepositional

Заодно means something like:

• while I’m at it
• at the same time
• since I’m already there
• in the process

In this sentence:

• зайду в аптеку и заодно куплю хлеб
• I’ll stop by the pharmacy and, while I’m at it, buy bread too

It implies that buying bread is an additional convenient action, not the main purpose.

A few similar examples:

• Пойду в магазин и заодно куплю молоко.
  • I’ll go to the store and buy milk while I’m at it.
• Раз уж ты там, заодно позвони мне.
  • Since you’re there anyway, call me too.

Куплю is the perfective future of купить, and it fits because the speaker means a single completed action:

• I will buy (and finish buying) bread

In Russian, perfective future is very common for one-time future actions.

Compare:

• куплю хлеб = I’ll buy bread
• буду покупать хлеб = I’ll be buying bread / I will buy bread repeatedly or as a process
• покупаю хлеб = I buy bread / I am buying bread, depending on context

Here the meaning is a simple plan: stop by, buy bread, go home. So куплю is the natural choice.

Изредка means:

• occasionally
• from time to time
• once in a while

It is correct and fairly common, though a bit more bookish or neutral than some everyday alternatives.

Other possibilities:

• иногда = sometimes
• время от времени = from time to time
• изредка = occasionally / now and then

So:

• изредка я так и делаю = I do that from time to time

It is not saying this happens often. It suggests irregular repetition.

In this sentence, так и делаю means:

• that’s exactly what I do
• I do just that
• I do that sometimes

Here так refers back to the action already mentioned: stopping by the pharmacy and buying bread on the way home.

The и adds emphasis. It often gives a sense like:

• indeed
• exactly
• just

So:

• изредка я так и делаю = occasionally, that’s exactly what I do

Without и, так делаю is possible, but так и делаю sounds more idiomatic and emphatic in this context.

Домой is a special adverb meaning:

• home
• to home / homeward

Russian often uses домой when someone is going home:

• иду домой = I’m going home
• по дороге домой = on the way home

Compare:

• дом = house/home as a noun
• в дом = into the house
• дома = at home
• домой = homeward / to home

So по дороге домой is the natural expression for on the way home.

In по дороге домой, the word дороге is in the dative case, because по often takes the dative when it means along, on, or by way of.

• дорога = road, way
• по дороге = along the way / on the way

So:

• по дороге домой = on the way home

Even though дороге looks the same as the prepositional singular form, here it is functioning as dative because of по.

This is a very common fixed expression.

Yes, but the meaning would shift slightly.

• после работы = after work
• с работы = from work

Compare:

• После работы я зайду в аптеку.
  • After work, I’ll stop by the pharmacy.
• С работы я зайду в аптеку.
  • From work, I’ll stop by the pharmacy / On my way from work, I’ll stop by the pharmacy.

So после работы focuses on time.
С работы focuses more on the starting point or route.

Since the sentence already has по дороге домой, после работы works very naturally.

No, Russian word order is fairly flexible, but changing it can affect emphasis.

The given order:

• изредка я так и делаю

is natural and means something like:

• Occasionally, that’s what I do.

Other possible orders:

• Я изредка так и делаю.
• Так я и делаю изредка. — possible, but less neutral

Putting изредка first highlights the frequency: occasionally.

So the original version sounds smooth and natural.

Yes, it is important. Both verbs describe single completed future actions:

• зайду = I’ll stop by
• куплю = I’ll buy

Perfective verbs in the future often express a clear sequence of completed steps. That fits the sentence perfectly:

1. after work
2. I’ll stop by the pharmacy
3. I’ll buy bread
4. I’ll continue home

If imperfective forms were used instead, the meaning would sound more like process, repetition, or a less bounded action.

So the perfective pair helps make the sentence sound like a concrete plan.

The semicolon connects two closely related ideas:

1. After work I’ll stop by the pharmacy and buy bread
2. I occasionally do that on the way home

A semicolon is stylistic punctuation. It shows a stronger break than a comma, but keeps both parts linked more closely than two separate sentences.

In everyday writing, you might also see:

• После работы я зайду в аптеку и заодно куплю хлеб. Изредка я так и делаю по дороге домой.
• or even with a dash in some contexts

So the semicolon is correct, but it is more about writing style than grammar.