Is this a 2-way integration?
No. This integration enables you to send Invoices from Productive to Xero, but not the other way around.
Do invoices get sent automatically or do I need to do it manually?
If you want to send an invoice from Productive to Xero, you need to manually click Send invoice to Xero on each Productive invoice.
Can I change account codes after I have completed the integration?
No, if you want to change account codes you need to delete the existing integration and start the process again.
Are there any requirements to setup the Xero integration?
You need to be a Productive account Admin. That's the only requirement.
Can I delete the integration to Xero?
Yes. You can completely delete a Xero integration. Explained here.
What happens if I disconnect the integration? Will I lose any data?
No, everything will stay as it is, you just won't be able to copy invoices to Xero anymore.