Accusative (m.)

Some of these are not in genitive, it's so-called partial (I'm not sure about the English term for it) case, that is not taught in Russian schools and linguists still have discussions regarding it. It is used to refer to "some quantity" of something, often food or drinks, in sentences like Give me/I'd like some tea/coffee/soup, etc. The endings are as in genitive. But in the same sentences if you don't mean "some", i.e. if you mean "give me tea (and not coffee) you will use accusative. Try to mind that difference.

Thus:
"Partial", endings as in gen (m.)
Дайте ему хлеба (+а)
Я не хочу чая (й=>я)

Я не хочу киселя (ь=>я) (кисЕль is a drink made of berries with starch)

Genitive (f.)
Вы хотите воды? (а=>ы) this one is "partial again (some water) if you ask "do you want water (and not milk)?" you say Вы хотите воду? (in acc.)
Собака Сони (я=>и) +
У меня нет кровати (ь=>и) +

Genitive (n.)
Крыша здания (е=>я) +
У моей (f.) комнаты нет окна (о=>а) +
 Genitive is most often used to say there is no something or that something belongs to somebody or is a part of something, as in your examples about the dog, the bed, the building and the window

Everything below is correct) Very good)

Prepositional (m.)
На столе чашка (+е)
На мосту медведь (+у)

Prepositional (f.)
На траве продукты (а=>e)
Он читает книгу о земле (я=>е)
На кровати лежит мяч (ь=>и)

Prepositional (n.)
На окне птица (о=>е)

Dative (m.)
Я дал книгу Ивану (+у)
Кто продал Сергею эту машину (й=>ю)

Dative (f.)
Каждый месяц Наташа пишет Тамаре (а=>е)
Каждую (f) неделю Наташа помогает Соне (я=>е)

Remember that дать и хотеть generally require objects in acc.

Russian declension memorization practice