2. Nitration is substitution of a nitro group into the aromatic ring

3. By Freidel Crafts acylation.

4. In nitration it is the nitronium ion NO₂⁺ . In sulphonation it can be SO₃ or SO₃H⁺. In halogenation it is an adduct with FeCl₃ which is Cl⁺-Fe^-Cl₃. In alkylation it is an adduct if it is a primary alkyl halide or a carbo cation in the case of a secondary or tertiary alkyl halides , and in acylation it is the acylium ion.

5. A Lewis acid is an electron pair acceptor, it has a vacant orbital. Examples, BF₃ or H⁺