I'll try to answer your questions one by one.
- If we go with Revolution Pi Connect +:
* Can the second LAN port be used for 2 common LAN networks (as shown up)? --> yes
* Main LAN switch will give every device an IP address regardless of cisco switch? --> I can't see from your description where your network gets the IP address. You can also assign fixed IP addresses on the device.
* Will this work --> In principle, nothing speaks against
- Another possibility to use new RevPi Compact:
* Is it possible to connect somehow an expansion DIO module to it? --> no
* If no, can its analog inputs be userd as 24VDC digital inputs? --> no
* Is it possible to connect them all in a chain --> yes, if no great demands are placed on the cycle time of the exchanged data
* Will this work? --> what exactly of it now
- If we go with RevPi Cores only:
* Can they be connected in a chain using a RevPi-Gate --> Depending on what exactly you have in mind, you could configure one unit as a Modbus TCP master and attach Modbus TCP gateways to the rest of the units. Daisy-chain cabling would then be possible.
* If yes, which network procol to use, and will there be any delay/strain on individual devices --> each gateway in the chain generates a delay
* If no, can they be connected in a chain in any other way? --> Not really a practical one, unless you use an external master, e.g. an EtherCAT master, and use the RevPis as EtherCAT slaves with the help of the gateway.
* Will this work? --> It depends on what your requirements are in terms of cycle time and data volume. At the moment, it looks to me as if the variant with the Connects is the much nicer one.
It would have been a little easier if you posted the questions as text and not as a picture. Then you can quote your questions and don't have to type them out.