What are the role of dry ether and AlCl3   in the Friedel -Crafts Alkylation.

No ! all the benzene derivatives are aromatic , but to be aromatic it's not necessary for a compound to be derivative of benzene. A compound needs to follow Huckel's rule to be aromatic

You ca take examples like Furan , Thiophene, Pyrrole etc.

The conditions required for an organic compound to become aromatic are:

• The compound must be cyclic
• It should be planar (2D) i.e. have sp² hybridization of carbon
• Delocalization of pi-bonds must be possible.
• Huckel's rule of 4n+2 must be satisfied.