yes, in the sense that their forward voltage, the voltage drop, is relatively constant and cannot be decreased by more gate drive.

yes,





if you see the characteristics of SCR, in forward region,( i have take 0 volt on gate for simplicity) the current is very small before some voltage . after certain voltage SCR conduts heavily. and comes in saturation region





now when some +ve voltage is applied at the gate, the voltage needed to put SCR in saturation decreases.





one thing is that you can find any state of a particular component by noticing characteristics levels of voltage and corresponding current

SCR while at DC mode ,as it is fired and become at conduce stage, it is saturated.

No, they can break down, but not saturated in the sense transistors do in some circuits.