no, you can't...

I tried to install Sailfish proper way (no warranty void message), but everytime I try so, it still is there!
It goes thru normally, but after when I install Openmode the warning is still there

The flasher option "--suppress-warranty-warning" has nothing to do with device open mode warning.

That option only suppresses the warning that flasher gives to you when you start it:

WARNING: This tool is intended for professional use only. Using it may result
in permanently damaging your device or losing the warranty.

@valexi you need to erase CAL before flashing open kernel to remove warranty screen

Is there any change that the bad outgoing sound from Sailfish phone - due to N9 port have learned! - can be improved in future OR is it same nearly unsolving issue as in NITDroid?

Looks like the enthusiasm for porting to the N9 has already fade away...

I feel like it's more that Jolla has not released any updates in the past few weeks, and so porting it to the N9 is not going go any further until they release something. There are lots of bugs that need to be addressed.

There are lots of bugs related to nemo hw adaptation and unrelated to sailfish.
According to this post, maybe 1.0.2.5 will last version of sailfish seen on N9.

http://talk.maemo.org/showthread.php?t=92431

I'm no expert on this matter but judging by the above link I think it more up to the community than Jolla.

Also check the bug tracker for the N9/N950 port to see whats still missing from the current port and these are something that Jolla can't help with, it's mostly up to the community:

https://github.com/romu70/sailfish-for-other/issues

I don't know if there are still developers doing much porting and solving the issues. I really hope so as a N9 user but I haven't done any coding since 2005 and my unix skills are close to non-existent so...

This seems to be end for sailfish porting on N9, Also for many days there is no news on update as it was during early days of the thread,
Sad for me and other N9 users