Let us go through your questions one by one
Now i need to log the errors which occur in the JS to my local drive.
First at server side, you would need to write a web service which would takes request from client and writes to file in your local drive(this would be your custom application log file and not ULS log)
Second on client side, write a common ...
If you are married to .NET Core your only real option is the REST APIs, and you are going to have to wire up all the code infrastructure and authentication yourself.
So, not impossible, but a bit lower level.
You can troubleshoot this issue as following:
Make sure that the account who open the InfoPath form has enough permission to access the “not exist” list.
Try to customize the InfoPath form without change via clicking “Customize Form” button and republish it, check again.
If the issue still occurs, I suggest you check the ULS logs, which would tell you more ...
After half day digging into this issue, finally I found the problem, the AutoSPInstaller creates the managed paths per web application but also creates with the HostHeader parameter which means (according to the New-SPManagedPath) that the managed path applies to all host header site collection.
So, to remove it I used the code below:
Regarding this issue while creating dropdown(choice) Column. In column setting select default value by choice and keep that field empty by deleting content in it .so after that while creating item it will show error message as "You can't leave this blank".
Tryed all solutions above, and nothing worked. The link below ended up working for me.