Can general compartment tickets (2S) be booked online? If yes then on what website?
No. General compartment tickets can only be bought at the local railway station. Although there is no information which specifically suggests this in the Indian rail booking portals web site https://www.irctc.co.in/beta_htmls/term_src.html#Q1, but if one goes on to the website and tries to buy a general compartment ticket, there is no option to do so. This answer here may also give more insight.