In theory you could say "On mógł był zrobić obiad", but that's plusquamperfekt and isn't really used nowadays. So we'd rather treat it just as if it was simply Past Simple - "On mógł zrobić obiad".
Is the perfective zrobić always used with the conditional? And if so is this the pattern with all such constructions?
No, absolutely not always, it can be used with other modals, it can be used in Future Simple, it can be used in the Past Tense...
I meant to ask if it was always On mógłby zrobić and never On mógłby robić when in the conditional.
Oh, this. No, it could be both. Whether you mean that he should finish this lunch or whether you just refer to the process, or making lunch generally (often, always?), not just on one occasion.
Im polish. I dont know any person who would say "lunch" as "dinner". In polish language long time wasnt word "lunch" it comes from West. "Lunch" is more like "drugie śniadanie" (second breakfast). And "obiad" you can eat only by yourself in home, not always with family or in restaurant. "Dinner" is a better option for "obiad" than "lunch", I promise ✌
Obiad is the main meal of the day, usually eaten around midday (12PM to 4PM). It is usually translated as lunch (because of the time of the day when it is eaten), sometimes as dinner (since it is the main meal which is often eaten socially – with family members, in a restaurant etc.)
Kolacja is a medium-sized evening meal, usually eaten between 6PM and 9PM. Again, since the conventions for naming a meal of this kind in English vary, it can be translated in two ways: as dinner or supper.
Eating habits vary between countries, and a simple equation doesn't work here. Even we British can't agree when we have dinner. For me, at the time "obiad" is eaten, I have (perhaps a late) "lunch". But although there are many in Britain who would call this "dinner", the only time I have dinner in the middle of the day is on Christmas Day.
I think most Americans would understand dinner to be an evening meal, and this seems to be increasingly the case in Britain too. Many will call their evening meal "tea", others "dinner". It seems however, that the word "supper" is in decline.
So I generally agree with Emwue. Duo have probably got it right here.