Question

Can it be said that in backbonding a substance behaves both as a lewis acid as well as a lewis base?

Answer 1

We can say like what you wrote. In back bonding , ​The Lewis acid should have electron deficient atom and lewis base should have lone pair of electron as well as have high electronegativity.
Also see my previous answer for further clarification.....
In the bonding atoms, one is a Lewis acid i.e., it should accept electrons and the other should be a more electronegative atom. This electronegative atom attracts the bond pair electron towards itself, at the same time due to its excess electron, it donates to the Lewis acid behaving like a base. For ex BF₃, in whihc B is Lewis atom and F is the most electronegative atom.