Are Acts of Worship Multiplied During the Last Ten Nights of Ramadan?

We don’t say that they're multiplied. Rather, we say that they're magnified. Meaning, their impact is more. Just like Sadaqa (charity) before the Fath (the conquest of Makkah) isn't the same as Sadaqa after the Fath. So, good deeds in the (last) 10 nights (of Ramadan) are not the same as good deeds on other days. Not in terms of its quantity, but in terms of the quality. And Allah the Almighty knows best, and may Peace be upon our prophet Muhammad.