Thanks, I get that, I really do but this is exactly why I was so much looking forward to Duo's Polish tree so that I wouldn't have to use a million scattered resources. I really only have time to study now on my phone on the bus to and from work due to other commitments.
I have to say, I'm quite disappointed with the tree because I'd hoped they'd find a way to do what others haven't been able to, which is to introduce Polish grammar step by step in a logical manner which allows us to learn the rules and practise without it becoming overwhelming. I've basically given up as I can't get past the genitive for negative sentences or the plurals without at least some guidance. I'll come back to it but maybe later.
Accusative is used for confirmation, Genitive for negation. But Accusative case in plural may often look the same as Genitive case in singular:
- lubię kaczki (!) - accusative plural ; lubię kaczkę - accusative singular
- nie lubię kaczek - genitive plural ; nie lubię kaczki (!) - genitive singular
EDIT: full list od declension types
KACZKA ż III
|Case PL||Sample questions||Case EN||singular||plural|
|Mianownik||kto? co? (jest)||Nom.||kaczka||kaczki|
|Dopełniacz||kogo? czego? (nie ma)||Gen.||kaczki||kaczek|
|Celownik||komu? czemu? (się przyglądam)||Dat.||kaczce||kaczkom|
|Biernik||kogo? co? (widzę)||Acc.||kaczkę||kaczki|
|Narzędnik||z kim? z czym? (idę)||Instr.||z kaczką||z kaczkami|
|Miejscownik||o kim? o czym? (myślę)||Loc.||o kaczce||o kaczkach|
In Grammatical Dictionary of Polish: http://sgjp.pl/leksemy/#6647/kaczka
No. If you like something, the thing that you like should be in Accusative case (no matter whether you like to hug it or to eat it).
The only difference is that when you like to eat it, then it is uncountable, hence no plural would be used: "lubię kaczkę" (I like duck).
If you like, for example, to watch the ducks swimming in a pond, you would probably prefer to say it in plural: "lubię kaczki" (I like ducks). Unless you mean a particular duck, which, is for example, your favourite pet, or toy. Then singular is also OK, but then you should indicate which duck you like, to make it clear that you do not plan to eat it: "lubię tę kaczkę" (I like this/that* duck).
*) Polish pronouns "ten/ta/to" (and declension thereof) can be translated either to "this" or to "that". A broader explanation here.