Not that I have ever grown okra from seed (doesn't grow well here and I actually detest the vegetable) but just Googling 'harvesting okra seeds' should provide all the info you need.

No, the seeds from frozen okra will not be viable. For one, they have been processed and flash frozen, which would limit their viability to begin with. Second, okra seeds are produced from very ripe, no longer edible pods that are allowed to dry and burst. Edible okra pods will not have ripe seeds. Either purchase fresh seeds or grow from starts.