Also stock only reduces after close cash - I think
try changing import com.openbravo.pos.payment.PaymentInfo; to import com.unicenta.pos.payment.PaymentInfo;
Do you mean send by email or something else?
Under maintenance/roles and unmark unwanted payment method for each role as rewuired. e.g.
see this link https://sourceforge.net/p/unicentaopos/discussion/1126900/thread/3b506371/?limit=25#8cdb
Yes can only be done modifying code base and database table structure.
This can be achieved via scripts. You will need to edit the printerticket resource and place a duplicate ticket but change printer to printer 2 or whatever you require. If you do a search you will find solutions.
A script won't work - you will need to edit source code.