Because a 2d subshell would require both n = 2 and l = 2, which is not an allowed value of l for n = 2, a 2d subshell does not exist.

Is a 2d subshell possible?

In the 2nd energy level, electrons are placed only in the 's' and 'p' sublevels, so there is no 'd' orbital. i.e. The second principal energy level consists of two sub-shell which is 2s (ℓ=0) and 2p (ℓ=1). So, 2d orbital can't exist.

How many orbitals are in 2d sublevel?

P sublevel has 3 orbitals. 2nd level has 4 orbitals. An f sublevel has 7 orbitals.