Microsoft changed install and registry location for vs2017 and original ISC EF installer will not be able to install VSTools to vs2017. You can use Code First, but if you need VSTools try VS2015 or wait for IRIS 2019.1. I do not know when it will be released, should be soon.
Full EF VSTools support for VS2017 will be released with IRIS 2019.1 .
Before making any change Studio will lock document. If lock fail document will not be edited and marked as "read only". All edits local. Save file will release lock on the server after save complete.
It can be CSP or URL
You can just use studio. Add your class/csp/routine to project, set breakpoints and Debug Target, save project and start debugging by Debug->Go
Yes to 2016.1. This is server side problem already corrected by MAK4540, not sure to what versions correction will be ported to.
Then it is a bug. What is client version and how to reproduce it?
Edit: this i s a bug for classes inherited from Ens.BusinessProcess. We will work on it.