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?
May 22, 2010 two pizzas (A value of about $40) were exchanged for 10,000 BTC.
At that exchange rate, $1000 of BTC would be 250,000 BTC.
At that time, there were about 2,852,150 BTC in existence.
So, acquiring 250,000 BTC would mean acquiring about 8.8% of all existing bitcoins.
Could it be done? I didn't know about Bitcoin yet in 2010, so someone else would probably be better able to answer. My guess is: Maybe. Probably not all in a single purchase though. You'd probably have to complete transactions with many individual. But to create such a large sudden demand would probably have driven the price up pretty quickly. In the end you'd probably have ended up with a lot less than 250,000 BTC as each individual purchase would significantly reduce the pool of bitcoins available for purchase and result in a higher price for the next purchase.
This answers the question in full.
I'd like to add that the first large bitcoin exchange Mt. Gox was launched in July 2010, so before that date it was almost impossible to buy bitcoin in large quantities, like the mentioned 250k.
To give you a perspective, the price at launche on Gox was around $0.06 and the whole exchange held less than 1% of the supply. This means that even if you were to use the largest exchange on the market in Q3 2010, you'd have a hard time buying $1k worth of BTC.