Learn Russian: Я не помню, зависит ли наш проект от погоды. - I don't remember whether our project depends on the weather.

The particle ли always comes immediately after the exact word you are asking about. Because you are wondering about the action itself (does it depend or not?), the verb зависит comes first in the clause, and ли attaches directly to it.

Can I use если instead of ли here, since we often say 'I don't remember if...' in English?

No, this is a very common mistake for English speakers! The word если is only used for conditions (like 'If it rains, we will stay home'). When 'if' means 'whether' in an indirect question, you must use the particle ли.

Why is it от погоды instead of using the word на (on) for 'on the weather'?

The verb зависеть (to depend) always pairs with the preposition от (from) followed by the genitive case. Russian literally says a project 'depends from' the weather. Because от forces the genitive case, the feminine noun погода changes its ending to become погоды.

Is the comma before зависит mandatory?

Yes! In Russian, you must always put a comma before a subordinate clause. Since the indirect question is a new clause within the sentence, the comma is absolutely required to separate it from Я не помню.