yes it is possible but first of all you have to find the exchange who have big volume market for buying bitcoin because with small exchange there will be difficult to buy large BTC amounts maybe bitfinex or kraken is good place to do so
Yes indeed but you could also buy from multiple exchanges I don't see why that would be a problem maybe the fees.
Or you could find a local reseller they make their own rules so probably some would sell you very big bulk amounts.