For sure upload add-on works with 2.1 as it works with at least
ver. 2.0.5 (2.0.5 is smaller than 2.1).
See this thread
related to the easy upgrades from the previous releases.
You would get an electronic invoice if you would pay on 2checkout. We ourselves do not provide business invoices since we are not a company but only a group of individuals. We accept Euros and yes, you can pay by bank transfer since we are located in EU; but you will also pay all transfer fees in this case. If you would like to do so, use our contact form
to email us privately, we will respond back on the address you provide.