"mięso" is neuter (like "dziecko") and "twój" should be inflected into "twoje" (twoje dziecko, mięso, krzesło, zwierzę - all of them are neuter)
Yep, "-o" is the most common suffix, and sometimes "-e" (stworzenie, pole, morze)
Twoje is neuter and must agree with the neuter noun. Generally, nouns that end in -o are neuter.
twój/twoja/twoje/twoi etc- belonging to you=1 person
wasz/wasza/wasze/wasi etc - belonging to you = 2+people
mój, twój, nasz, wasz- my, your, our, your(plural)- describing a singular masculine noun in nominative case, or singular masculine not animated noun in accusative case.
moje, twoje nasze, wasze - describing singular neuter noun in nominative or accusative case; describing a plural not masculine personal noun in nominative or accusative case
Duolingo algorithm sometimes puts one sentence from a totally different skill into your lesson. Nothing we can do about it, there's no point in complaining. Theoretically it's a random check of whether you still remember it.
Okay, so I answered a question and also stated a fact that there's no point complaining if someone wanted to complain ;)
Maria, is the other difference of informal vs formal? It seems very similar to Russian, where you use one with a friend and the other with your teacher, boss etc...
However it's not. It's only the difference between singular and plural. Using "wasze" when talking to a single person will seem very weird (although there's quite a chance that your interlocutor will understand that you confused Polish and Russian).
In formal speech we refer to a man as "pan", to a woman as "pani", and then there's "panowie" (gentlemen), "panie" (ladies) and "państwo" (mixed gender plural). It's used with forms of 3rd person - singular or plural, respectively. You will encounter it later during the course.
The form of possessive depends on the gender of the noun it describes (and the case). But staying in Nominative, like this simple phrase here, you have:
twój (masculine): twój dom
twoja (feminine): twoja książka
twoje (neuter): twoje mięso
twoi (masculine personal plural): twoi rodzice
twoje (not masculine-personal plural): twoje psy
Not sure if you had plurals already or not.