Who discovered the synthesis of $DNA$ from $RNA$ in Rous sarcoma virus?

Which of the following statements is incorrect $:-$

Which of the following statements is correct about $DNA$ polymerase?

The direction of $DNA$ replication is .........

Which bonds does helicase break in $DNA$?

$A$ $DNA$ molecule containing radioactive thymidine is allowed to replicate in a non-radioactive environment. What will be the exact number of $DNA$ molecules containing radioactive thymidine after three replication cycles?