Will I be able to have level 2 (7 kw) charging by plugging the level 1 charge cord (with the appropriate adapter) directly into a 240 vac , 30 amp receptacle without installing a separate level 2 home charger?
What is described above is the "granny charger" which allows you to charge at home (or wherever) without a dedicated charging station. However, such chargers typically do something like 1.3kW, not the 3.7/7.2/11/22 kW you can do on a real charging station.
If you have a space to park & charge at home, I highly encourage you to have a dedicated charging station installed. The granny charger is such a hassle that in practice you will not use it. Consider it a last resort in case you're stranded somewhere. In my 4 years of owning a Leaf, I've used it maybe 4 times, of which 3 times it blew out a fuse (on the socket/house, not the car). It's pretty useless.