You sure about the 90s? Not saying it was impossible, but must have been extremely rare. Arclight was one of the first theaters to do assigned seats in 2002. AMC only started trialing in 2008, but didn't start rolling it out until 2016 in NYC.

Totally possible, was through a central phone number in The Netherlands called "BelBios" ("CallCinema"). You were guided through the different movies and showtimes, pressed the numbers, and got a booking code. You then went to the cinema, provided your booking code and paid.

In the US perhaps. Seat reservation has been the norm here in Norway since at least the 80s.