One switch, two switches.... any number of switches is EQUALLY safe if you know how to connect them
This sentence is not possible to understand. Please make a drawing or explain.
A limit switch should be normally closed, not normally open. ANY number of NC switches can be connected in series and they are just as safe as one switch. I don't understand by what you mean, why would it be safer to use one switch, as opposed to two, or even six, like I have it connected.
If the circuit is broken for ANY reason (lose or broken wire, machine overrun, switch fell off...
wire cut, running off the rail... whatever) the limit circuit will trip and the machine will stop even if you have more than one switch. Using only one switch on each axis is possible, but more complicated than using one on each end of the same axis. Of course, you MUST connect the switches in series and use normally closed type.
What you mean by
"limit switch which is turned on by force during whole path"? If you turn ON a switch it means you make contact, that is very wrong, for safe function the switch must be on ALL the time and turned OFF by force, which should be detected by your circuit and stop the motion. It is important to use the right terms, otherwise it is easy to misinterpret and create confusion.