Навіть якщо графік відключень змінять, ліхтарик готовий.

Not quite.

• якщо = if
• навіть якщо = even if

So навіть adds the idea of regardless of whether this happens. It makes the condition weaker in importance: the main point still stands.

Here, the idea is:

• even if the outage schedule changes,
• the flashlight is still ready.

Because Навіть якщо графік відключень змінять is a subordinate clause introduced by якщо.

In Ukrainian, clauses introduced by якщо are normally separated from the main clause with a comma.

So the structure is:

• subordinate clause: Навіть якщо графік відключень змінять
• main clause: ліхтарик готовий

If you reversed the order, you would still use a comma:

Ліхтарик готовий, навіть якщо графік відключень змінять.

This is a noun phrase meaning something like outage schedule or schedule of shutoffs/outages.

• графік = schedule, timetable
• відключень = of disconnections / outages

Very often in real-life Ukrainian, відключення in this kind of context refers to utility shutoffs, especially electricity outages.

So графік відключень is literally a schedule of outages.

Відключень is the genitive plural form of відключення.

That happens because графік often takes another noun in the genitive to mean schedule of ...:

• графік роботи = work schedule
• графік поїздів = train schedule
• графік відключень = outage schedule

Why plural? Because the schedule usually contains multiple outages, not just one.

So:

• singular dictionary form: відключення
• genitive plural here: відключень

Змінять is 3rd person plural future of змінити.

Literally, it means they will change. But in Ukrainian, just like in many languages, 3rd person plural can be used with an unspecified subject:

• змінять = they will change it
• meaning: some people, the authorities, the company, whoever is responsible

English often does something similar with they, even when we do not mean specific people.

So the sentence does not need to name the subject. It is understood from context.

That is a very common question.

In English, future conditions usually use the present tense after if:

• If they change the schedule...

In Ukrainian, using the future tense after якщо is normal when the action is really in the future:

• якщо змінять = if they change / if they will change

So this is not a mistake or something unusual. Ukrainian and English simply handle if-clauses differently here.

Because the sentence is talking about a single completed change of the schedule.

• змінити → змінять = to change, complete the change
• змінювати → змінюватимуть = to be changing / to change repeatedly or over time

Here, the natural idea is:

• if they change the schedule,
• meaning if they make that change and the result is a new schedule

So змінять fits better than an imperfective future, which would sound more like an ongoing or repeated process.

Because in the present tense, Ukrainian usually leaves out the verb to be.

So:

• ліхтарик готовий literally looks like flashlight ready
• but it means the flashlight is ready

This is completely normal in Ukrainian.

You can think of it as:

• English: The flashlight is ready
• Ukrainian: Ліхтарик готовий

The meaning of is is understood automatically.

Because готовий agrees with ліхтарик.

• ліхтарик is a masculine singular noun
• so the adjective must also be masculine singular
• therefore: готовий

Compare:

• ліхтарик готовий = the flashlight is ready
• лампа готова = the lamp is ready
• пристрої готові = the devices are ready

So the ending changes depending on the noun’s gender and number.

Yes.

You could also say:

Ліхтарик готовий, навіть якщо графік відключень змінять.

That keeps the basic meaning.

The difference is mostly emphasis:

• Навіть якщо ... , ліхтарик готовий puts the condition first
• Ліхтарик готовий, навіть якщо ... puts the main message first

In your sentence, ending with ліхтарик готовий sounds a bit reassuring and emphatic, as if that is the important conclusion.