По выходным бабушка любит обедать на даче под липой.

In Russian, по + dative is often used for repeated time periods:

• по утрам = in the mornings
• по вечерам = in the evenings
• по выходным = on weekends

So по выходным does not mean one specific weekend. It means something like on weekends / at weekends / every weekend as a general habit.

Because it is dative plural.

The basic word is выходной, which originally means day off or weekend day. In this phrase, Russian is really using a shortened version of:

по выходным дням = on weekend days

The noun дням is usually omitted, and выходным stays in the same form.

So:

• выходной = weekend/day off
• выходным = dative plural, required by по in this time expression

Russian has no articles, so there is no separate word for a or the.

Бабушка is in the nominative case because it is the subject of the sentence — the person doing the action.

Depending on context, бабушка could mean:

• grandmother
• the grandmother
• a grandmother
• more naturally in English, often grandma

English has to choose an article; Russian usually does not.

Because after любить when you mean to like/love doing something, Russian uses the infinitive.

So:

• любит обедать = likes to have lunch / likes having lunch

This is the same pattern as:

• любит читать = likes to read
• любит гулять = likes to walk
• любит готовить = likes to cook

A conjugated form like обедает would mean she has lunch, and it would not fit after любит here.

Not exactly. Обедать means to have lunch or to eat the midday/main meal.

Compare:

• есть = to eat
• обедать = to have lunch
• ужинать = to have dinner/supper
• завтракать = to have breakfast

One extra nuance: in Russian culture, обед can sometimes mean the main cooked meal of the day, so it may feel a little broader than English lunch in some contexts. But for most learners, обедать = to have lunch is a good starting point.

Because обедать is imperfective, and that fits a habitual/general preference.

Here the sentence is about what grandma likes to do regularly on weekends, not about one completed lunch.

• обедать = to have lunch, in general / repeatedly
• пообедать = to have lunch once, with completion

After любить in this kind of meaning, the imperfective is normally the natural choice:

• любит читать
• любит гулять
• любит обедать

Because на даче is the normal Russian expression for at the dacha / at the country house.

A дача is a country house or summer cottage, often associated with a garden, weekends, and time outside the city.

Case-wise:

• на даче = prepositional, meaning at/on the dacha as a location
• на дачу = accusative, meaning to the dacha (destination)

So:

• Бабушка обедает на даче = Grandma has lunch at the dacha
• Бабушка едет на дачу = Grandma is going to the dacha

As for в даче, that is generally not how Russian talks about being at a dacha in this everyday sense.

Because под can take different cases depending on the meaning:

• под + instrumental = location, under
• под + accusative = motion, to a position under

Here grandma is already sitting/eating under the tree, so it is location, and Russian uses the instrumental:

• под липой = under a linden tree

If someone were moving to that spot, you could use the accusative:

• сесть под липу = to sit down under the linden tree
• пойти под липу = to go under the linden tree

Also, липа is a linden tree (not a citrus lime).

Yes. Russian word order is fairly flexible.

The version here:

По выходным бабушка любит обедать на даче под липой.

sounds quite natural and neutral, with the time expression first setting the scene.

You could also say:

• Бабушка любит по выходным обедать на даче под липой.
• Бабушка по выходным любит обедать на даче под липой.
• На даче под липой бабушка любит обедать по выходным.

These are all possible, but the emphasis changes a little.

Very roughly:

• first position often gives the topic or what the sentence is framed around
• later positions often get more focus or sound more emphasized

The standard stress is:

По выходны́м ба́бушка лю́бит обе́дать на да́че под ли́пой.

Key stresses:

• выходны́м
• ба́бушка
• лю́бит
• обе́дать
• да́че
• ли́пой

This is useful because Russian stress is not fully predictable, and wrong stress can make a word hard to recognize.

It describes a habit.

Several things signal that:

• по выходным = on weekends, regularly
• любит = likes to
• обедать = imperfective infinitive, used for repeated/general action

So the overall sense is not this weekend grandma is having lunch... but rather as a usual pattern, grandma likes having lunch there on weekends.