You don't need that synth to make that sound - you can make it in practically every synthesizer on the market, if you're willing to take the time and effort to translate the information onto your own softsynth. You could make it in Massive, Sylenth, Serum, FM8, Synth1, Razor, Harmor, 3xOsc (with some post processing), or really ANY synth that can output white noise, has LFOs, and has modulation envelopes.

There's no hot-key because the polarity is based on the waveform, not the LFO modulation range.

If you open Massive and click on any one of the LFOs, there are windows rightly to the right of the waveform display. Above them, it says "Curve Select". There are two dropdown menus below it - click on the top one and select one of those waveforms I previously mentioned! Now the modulation will only affect the green side of the modulation depth, instead of both!

Other good ways to get the future bass "flutter" effects:

• Draw automation curves on the filter you place over the super saw chords in the shape you want the flutter - this takes a lot of time and patience, but can create an incredibly expressive and lifelike sound
• Using a Tremolo at full depth, automate the rate of the tremolo. In Ableton, the Auto Pan with Phase set to 0.00° and the Amount set to 100% you get the same effect.
• Similar to the first idea, place a utility/gain/balance plugin on your track and automate the volume!

New Drum and Bass tune out for free download!

It's a combination of things, different for each sample pack designer.

sometimes they're made with synthesizers, sometimes they're sampled from other songs or old vinyl records then processed and changed so much that they're unrecognizable, sometimes they record things live and then process them, and sometimes they take samples from other sample packs then layer and process them together to become a new, whole sound!

Creativity is a muscle - Exercising it is required for growth, but without a direction to go and a plan for how to perform optimally you will always be hindered.

If you're having trouble writing melodies, spend a week practicing melody writing. Go back and work on your music theory chops - good melodies have a proper amount of chord tones, passing and neighbor tones, and occasionally other non-chord tones. Work on your ideas of contour, and make sure you have a destination in mind. Melodies that contain leading tones are often some of the best, too, so go back to your harmony and think about that as well.

Analysis is also your friend, here. Go find ten tracks that you think have well-written melodies, and bring them into your DAW. Try to recreate the melodies with MIDI and compare/contrast them: What do they all do the same? What do they all do that your melodies don't do? What do you do that none of these melodies do? How do they relate to the chords of the song? What is their contour?

If you can't access FL's Mixer, then you can't really do anything to any of your sounds (as far as I'm aware). You can just arrange things. If that's the case, you might have to try bouncing your arrangement to stems, then import it into another DAW and process your sounds there.