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?
It's possible since there were already exchanges around that year. Plus, aside from exchanges, you could also buy through P2P transactions.
Here’s a reply from one of the old members in the forum that should answer your question.
Buying BTC is easy today with sites like Coinbase but what was it like in 2010 and 2011?
New Liberty Exchange was up in 2009. Mt. Gox came up in mid-2010 and took up a lot of the market until its eventual collapse in 2014.
It was also more common for people to mine at home, because specialised hardware was not yet available nor required.
What wallet did people use?
Bitcoin Core. The blockchain was tiny then so it wouldn't have taken much effort (not that it really takes that much effort now).
you can also follow and read that thread for more information.
Yes you're right as Long as there's an exchange back then it can be possible to buy 1k bitcoin then, before you think of asking such question have you ever imagined how those early investors manage to invest in bitcoin back then? That's to prove to you that there's already an existing exchange and other means to buy bitcoin back then, though it just few exchange that was existing back then, it was not as many as it is nowadays, why most people was also using P2P.
I guess majority of those early investors was only familiar with P2P. moreover, I don't think if anyone will take the risk to buy bitcoin using such amount back then, because no one knows about the good potential in future, so they wouldn't want to risk such amount in something that the outcome is not guaranteed.