Practical use of M70 and M72 codes

Hello. Please explain to the pensioner the practical application of the M70 and M72 codes. Here is an example, but I can’t understand if I can return to the breakpoint of the control program after moving the tool from the breakpoint. If possible, how. Thanks!

Not sure what you mean by "breakpoint", but the use of M70/M72 causes no tool movement. However there may be a change in relative coordinate position, if the coordinate system was changed or offsets applied between the issuing of M70 and M72. In that case those setting will be returned to what they were when M70 was issued and the resulting changes in position reported will take affect (but no movement will occur).

you can use this M70 to change Spindle in a multiple Spindle mashine like a SAW and a BIT back and forth
this gives you the benefit of the CAM dont need to be setup all again in postrocess to a operation

or simply restore all after bitbreak detection to run from here

That is, I stopped the machine, say, to clean the cutter - the chips were wound. He brought him out of the working area, did everything that was needed.
1stop the program
2 remember the location of the instrument
2.1 for such purposes, I usually use the command to remember the place where the program stopped
MDI_COMMAND = G28.1
3 cube food is convenient for me to clean or even replace the cutter
4 to return to the starting position such commands
MDI_COMMAND = G53G0X [# 5161]
MDI_COMMAND = G53G0Y [# 5162]
MDI_COMMAND = G53G0Z [# 5163]
Well, then run the program with the selected line, after turning on the spindle,
for convenience, drawing the appropriate buttons on the panel. Instead of G28.1, can I somehow use the M70 and M72 to return to the starting position to go from here? Thanks for attention.

No, M70/M72, is not a means of resuming a program where you left off.

There is a component that can be set up in your config that would allow you to jog the machine while it is paused while executing a program, then return to the original paused position and resume.
www.linuxcnc.org/docs/2.7/html/config/moveoff.html
There are example simulation configs to demonstrate it's use.
But I've not tried it out myself.