These are the main standards:
This is only possible if one of the cable can run in NT mode (see glossary on what this is: glossary_ntmode). Only a few cards allow it, all others need an NTBA or PBX with an internal bus to communicate with each other. See question feature_crossedcable.
Yes. Both ISDN packages load the module isdn.o, otherwise the naming conventions are different. Tip: rename Urlichs isdn.o to uisdn.o, and change lib/modules/modules.isdn (or whatever the file is called that lists the modules and is read by the script) accordingly. Happily the default names of the ISDN devices are also different.