Hello, x_lil_ballerina_x, and welcome to CriticalDance! You sound very excited to take up your dance lessons again. I can't help you with the tap question, but the Cecchetti forth arabesque is described in Gail Grant's Technical Manual and Dictionary of Classical Ballet
as follows: "Forth arabesque: The supporting leg is nearer the audience and is in demi-plie. The arms and head are held as in the first arabesque with the arm on the side of the raised leg being forward." In other words, plie croise arabesque with the same arm raised forward as the leg lifted behind you...Hope this helps!