And answering your questions one by one:
1) I cannot find any description about implemented mach3 functions in uc300eth
It is implemented, but had was not woring in 1.006 plugin version.
2) I cannot find this function 'Digit/probe input' in uc300eth
There is the Probe input in the Mach3 setup. The plugins can't override the Mach3 settings, so it must be there in the ports and pins in the inputs config.
3) is there any way to get and make Firmware update not automatically for mach3 and uccnc ?
The firmware updates happens automatically in terms of that a plugin or if the UCCNC version requires a different firmware to run than what is actually installed into the UC300ETH then it will update the firmware. If the firmware version fits the plugin or the UCCNC version then it will not update the firmware.
The firmware versions check and update happens automatically and it must happen otherwise the device could not work properly with a non-matching firmware.
4) is there any description for setup the probe in uccnc?
I cannot find any description of Probe2. What does is mean, and how it is to setup?
If I set up Probe1 pin and start to probe, after stop in the first pass the z-axis doesn't stop after touch the probe-plate again.
Do I have to set Probe2 equal Probe1? why I must all this things investigate through try and error?
Probe 2 input is equivalent to the Probe 1 input. You can have 2 probes is what is Probe 2 is for.
The Probe 1. and Probe 2. work in an OR connection and both can trigger the same probe function (G31) in the UCCNC, so if any of the 2 probes activates makes the probe for the UCCNC to become active.
The advantage of having 2 probe inputs is that probes can have normally open and normally closed connections and if you for example have one probe (e.g. a touch plate) with NO connection and you have another probe (e.g. a 3D probe sensor) which has NC connection then you could not connect these 2 to the same probe input, because one has NO and one has NC connection, so you can't connect them in parallel and you also can't connect them in series to one probe input, because their output configuration is different. So, you need 2 probe inputs to connect both sensors the same time and you can do that, because the UCCNC has 2 probe inputs acting in an OR connection.