Which structure of $RNA$ resembles a cloverleaf?

The catalytic property of $RNA$ was discovered by:

Given below are two statements:
Statement $I$: $RNA$ mutates at a faster rate.
Statement $II$: Viruses having $RNA$ genome and shorter life span mutate and evolve faster.
In the light of the above statements,choose the correct answer from the options given below:

The most abundant $RNA$ found in a cell is .......

What is the full form of $rRNA$?

According to the discovery made in the $1980$s,$RNA$ can act like an enzyme to assemble new $RNA$ molecules on an $RNA$ template. Which of the following statements is not supported by this theory?