Ok,
that's clear now. Thank you.
I was not really sure because i read this post
https://forum.archive.openwrt.org/viewtopic.php?id=67607&p=1#p338569
and you can read, in the Villeneuve post (code block), that setting the current firmware partition, prior to flashing he can decide where to flash. ( so.. i think that setting current partition to number 1, he can flash on number 2)
If setting boot partition, decides also which partition NOT to flash, we have a way (only for OWRT) to flash where in which partition we desire..
Thank you