MAX 10 in place of Cyclone IV

All devices have at least enough flash to hold at least one copy of rhe logic of your design; some have only a tiny amount spare, some have lots spare (and by way of keeping the number of distinct devices reasonable, they've bundled larger flash size with the analog features, even though they aren't directly related.

Spare space if available can be used for:

• Keeping a second copy of your logic, to allow safe in-place upgrades (where the logic currently running is used to control writes to the flash containing the logic image)

• To initialise not only the logic but also the content of any RAM blocks you have used in your design (useful if you want a ROM look-up table, or perhaps if your design contains a soft CPU). This is what was being referred to above.

• As "UFM" (user flash memory) as a separate peripheral you instantiate - for similar purposes to initialised RAM, but slower and more awkward to access.

I don't have the datasheet in front of me, but IIRC the base 10M02 have particularly small flash size - just enough for one copy of the logic and a bit of UFM.

The documentation is a bit confusing- it implies that all the variants of a given device (10M02,10M04 etc) have the same amount of flash, but you just can't use some of the features that would need to use the extra flash sectors. Possibly it's a price/features licensing thing policed by the compiler tools; possibly the less-memory parts are binned from production of the same silicon.