Would it have been possible to buy 1000 usd of bitcoin in 2010 or earlier? If not then how to acquire this amount or more?
yes definitely, although most exchanges that served that year no longer exist.
Exchanges existed in the past where you can actually pay the quantity of btc you wanted but not quite a number of people believed btc until later in the year around 2015 when the price started growing rapidly.
I remember there was coinexchange which was one of the popular exchange but no longer existing.