Following the frequency hopping is possible if the hop pattern is known, i.e. follows a specific, static pattern. But if a secret key is used to generate the hop pattern, then you'd have to either know the key (maybe legal, depending on how you got it), or crack the encryption (possibly illegal, maybe impossible).
Any known modulation scheme can be demodulated in software, if the SDR can receive the frequency range has enough bandwidth to receive the entire signal simultaneously. For example, a RTL SDR can decode broadcast stereo FM, which uses 100KHz of bandwidth between 88-108MHz. But it cannot decode Wi-Fi for 2 reasons:
1. Wi-Fi uses a higher frequency range than can be received by the RTL SDR (2.4GHz, vs 1.7GHz upper limit for the RTL SDR), and
2. Wi-Fi channels are 20-40MHz wide, and the RTL SDR can only receive 2-3MHz of bandwidth at a time.
You would need to know the details of the hop algorithm, including whether or not some kind of user-defined key is used to generate the hop sequence.
Your SDR would have to be able to retune fast enough to follow the hops. That might require 2 SDR receivers, alternating between retuning to the next hop frequency and listening to the signal.
Your SDR(s) need to be able to receive the entire signal modulation bandwidth, but do not need to receive all possible hop frequencies simultaneously.
Lastly, you need software that can take the digital data from the SDR(s) and decode it properly. This may or may not currently exist.