Learn Russian: Эта новая булочная открыта или закрыта?

Булочная is a substantivized adjective. This means it is an adjective (literally meaning 'related to buns') that has taken on the role of a noun. Because it represents a shop, it takes the feminine adjective ending -ая. Even though it acts as a noun in the sentence, it will decline exactly like a regular feminine adjective in all cases.

Is булочная pronounced exactly as it is spelled?

Not usually! While spelled with -чн-, the traditional and most common pronunciation is було[ш]ная (with a 'sh' sound). This is a famous exception in Russian phonetics, just like the word конечно (of course).

Why do we use the short forms открыта and закрыта instead of the full adjectives открытая and закрытая?

We use the short forms here because they form the predicate of the sentence, telling us the current state of the bakery. In Russian, when 'open' or 'closed' describes a temporary state ('is open') rather than a permanent characteristic ('an open door'), the short forms are heavily preferred or required.

Do the modifiers Эта and новая treat булочная as a noun or an adjective?