Yes.
18 inch
No. You'd have to buy an adapter
Yes you can fit 20" rims on you 1979 cutlass, if you wanted to you could fit 22" rims with low profile tires with the stock springs.
Yes, a 1979 Firebird tail light will fit a 1979 Trans Am. There are also restoration services if you have the tail lights and they just need to be repaired.
Yes
YES.
Some parts will fit, depends specifically on what parts you're referring to
22 rims will not fit any ford escort.
no will not fit
Check the Firebird and Camaro seats.
Yes
A 1970 Firebird front bumper will not fit a 1979 Firebird without modifications. The two models have different designs, mounting points, and overall dimensions. While some components may be interchangeable, it’s generally advisable to use parts specific to each model year for proper fit and alignment.