Yes, they are different species and different genera, but they are both sold under the name 'Anacharis'. Egeria densa has broader, glossier, more tightly packed leaves; Elodea canadensis is somewhat more fluffy in appearance.
The plant in the last photo looks like a seedling Dracaena 'Massangeana', a popular potted plant sometimes called 'corn plant'. It will not do well submerged; if you want to keep it it needs to be taken out of the tank and planted in a pot with sandy soil; it can also be grown hydroponically, like the 'lucky bamboo' (also a Dracaena) sold at nurseries.