Several Roman Coins To Verify

The two first coins are indeed Constantius II, Gloria Exercitus type. The top one is minted in Lugdunum (today's Lyon in France; that is what the PLG at the bottom means: Prima officina [1st mint branch] LuGdunum). The bottom one is minted in Antioch, Syria (today's Antakya, Turkey; SMANZ stands for Sacra Moneta ANtiochiae 7th officina).

The legend around Constantius reads FL IVL CONSTANTIVS NOB C and is spelled out Flavius Iulius Constantius Nobilissimus Caesar. Nobilissimus means Most Noble, Caesar was at this time the title for the subordinate emperor(s). Constantine the Great was emperor over all of Rome and had the title Augustus (his coins have AVG at the end of the legend). His sons - Constantius, Constantine, and Constans - were all caesars.

The Probus coins are not folles, they are antoniniani (seen by the spiked crown). The mint for the top one is Ticinum (today's Pavia, Italy). It should be here (bust can be either left or right for this type): https://en.numista.com/catalogue/pieces292734.html
Also check OCRE for this type: https://numismatics.org/ocre/id/ric....386?lang=en

Mint for bottom Probus is either Cyzicus (https://en.numista.com/catalogue/pi...293262.html) or Siscia (maybe https://en.numista.com/catalogue/pi...93000.html).

The last coin is Postumus, as @oriole points out. An antoninianus, minted in Lugdunum. OCRE entry: https://numismatics.org/ocre/id/ric...t.58?lang=en

Many thanks for your help regarding these coins.

Is spiked crown always means that a coin is an antoninian? I mean is it a general rule for Roman coins?

This is certainly not an absolute rule. The radiate crown was used on middle bronze coins on dupondii (not all dupondii are radiate). Antoniniani were introduced in A.D. 215 by Caracalla and were used through to the monetary reforms of Diocletian. There are a variety of radiate coinage that occur post the monetary reform that use the radiate crown but these are not Antoninianii.

Example radiate dupondii
Vespasian

Maximinus Thrax


Example post reform radiate
Licinius

First one is Gordian III with Jupiter on reverse. Here is the OCRE entry, where you can also see full legends and other info: https://numismatics.org/ocre/id/ric...i.84?lang=en

Second one is Trajan Decius with Aequitas on reverse: https://numismatics.org/ocre/id/ric...d.44?lang=en

Forvm Ancient Coins has a lot of useful information about Roman and other ancient coins. Here is their page on Roman legends: https://www.forumancientcoins.com/n...6CtQWYv_c6-8