Presumably "TP - Target Practice Tracer" is the M220 TP-T (part of the M50 series) and "TP - Target Practice-Tracer PGU" I'm pretty sure is the PGU-30A/B TP-T (part of, as the name suggests, the PGU series).
The PGU series is newer than the M50 series (superseding it in the late 80s if wiki is to be believed), and AFAIK it has aerodynamic optimisations, reducing drag (thereby reducing time-of-flight and increasing velocity (and therefore KE) at the target, compared to the M50 series).
Personally, I wish ED would just name the actual round and the type of ammunition it is, it would make things so much easier, and this absolutely goes for CA too.
Going down the list it's as follows (at least AFAIK):
HEI-T High Explosive Incediary-Tracer: M242 HEI-T
HEI - High Explosive Incediary: M56 HEI (M56A3? A4? no idea)
AP Armour Piercing: M53 (though this is an API round, again - why ED should just name the round)
TP - Target Practice Tracer: M220 TP-T
SAPHEI High Explosive Armour Piercing PGU - PGU-28 (A/B?) SAPHEI
TP - Target Practice Tracer PGU: PGU-30 (A/B?) TP-T
M50 series (I guess currently produced, see here for the full table)
Northstar98's post in APKWS was marked as the answer
It was supposed to be 2002 IIRC. It might have some other stuff that is later, but even accounting for that, it still predates APKWS by a significant amount of time.
AFAIK, the new A-10C is ~2017, so Scorpion HMCS, APKWS and GBU-54 are all perfectly accurate. The older A-10C probably best fits circa 2005 AFAIK, which is why it doesn't have those systems.
I might be wrong, but I think the new security system is tied to your account, so as long as you're signed into a machine with your account, you should be able to install the modules, no problem.
They might have a check to make sure that 2 machines aren't running your account at the same time, but you should be able to install on both, you just have to make sure you're only signed in on one at a time - at least that's how I think it works.