>>64230877 (OP)
No, both FTF and jams are under the broader umbrella of weapon malfunctions, but the phenomena are distinct from each other.
FTF means a cartridge is in the chamber, striker or hammer drops, but there is no bang for some reason.
A jam means that a cartridge either fails to feed into the chamber, extract or eject.
A jam can potentially cause an FTF, but that's uncommon because most modern firearms don't allow the firing sequence to happen if not in battery. Theoretically this could happen with an open bolt firearm, since it fires as a result of dropping the bolt into battery against spring tension.
>>64231574
I think it's the same concept as having a bayonet lug. You don't really "need" it strictly speaking, but it isn't really difficult or expensive to add some flip up backup sights and they don't particularly get in the way when not in use. Everything can break, on a rifle meant for heavy use having backups is always a good idea. Sucks to have the effective range of a rifle cut to almost nothing just because your glass took a hit, the mount got knocked off zero or your battery overheated and fried your red dot. Having some flip up sights to fall back on can get you out of that situation.
Even if it isn't a combat rifle, I've seen people get screwed at a match because their scope came loose or while hunting because the rifle got dropped and the scope cracked. No backup sights in both situations meant the user had to switch rifles. Not the end of the world, but it would be a significant problem if they didn't have a backup rifle to switch to.
>>64236225
No, that can cause a pressure spike. Check all the cartridges, write down the lot number(s) off the boxes and reach out to CCI. This happens when the machine that seats the bullets goes out of whack, and it's something they really want to know about.
If you have a receipt from where you got that ammunition and what you paid for it, they usually cut you a refund check.