Yes, the MR20 has a 2.4GHz and a 5GHz radio. It doesn't have the third radio present on the MR33. The third Wi-Fi radio is used for:
While these features are available on the MR20 (except maybe for rf spectrum, i would have to check), it has to use its regular two radios for them, causing it to stop serving clients for very short times (mostly unnoticeable by clients in less busy networks).
So yes, you can set multiple 2.4 and 5GHz SSIDs. They will all use the same channel per band per AP though, so don't put too many SSIDs on a single AP. Recommendation is to not have much more than 4.
P.S. The MR33 also has a fourth Bluetooth radio for beacon detection that the MR20 doesn't have.