That is not (easily) possible. To copy the active instances over to your new server, you need to bring the database over and upgrade it to 10.4. This will bring over the old processes with it too. I think your best bet is to download the processes you've modified in 10.4, backup then move the database over to your 10.4 server, then re-apply the changes you made to the processes with active instances on them.
Although I don't recommend it, there is a way you could try and get what you're after. Forms 10.4 has the ability to overwrite processes with updated versions, but that relies on the process and each process element having the same GUID as the currently uploaded process. To try and take advantage of this, you could
- Download the updated processes you made in 10.4 (Process List A)
- Backup then migrate the 10.1 database with active instances to the 10.4 server (Process List B)
- Download those newly migrated processes and open up the process XML (Process List B)
- For EACH ELEMENT, copy the GUID from the Process List B process to the corresponding Process List A XML
- Now you should have updated your Process List A processes so that the GUIDs match what's currently in your Forms server
- When you try to upload a process from Process List A, it should ask if you want to overwrite the existing process
- Since you updated the GUIDs, the Process List A updates will overwrite the Process List B processes with active instances
If you do this all correctly, you can get your 10.4 changes to apply to the processes with active instances. Please back everything up though, because there are lots of GUIDs to copy and this would be rather error-prone.