Do you fail Veronicas quest if you use research items from vault 22 to finish "there stands the grass", instead of her quest? Or can you just collect another item for Veronicas quest?

Since I already had both the C-Finder and the pulse gun and didn't
want to risk triggering any glitch, I decided to retrieve the experimental technology
from Vault 22 and while at it, I thought I could as well go through 'There stands the grass'.

All went rather smoothly. I retrieved the research data from the vault mainframe
and when Keely realized that the data was downloaded already, she asked for it to
have it destroyed. At that point, if you have Veronica and her quest is active you
can tell Keely so and you get to move on peacefully.

You also have the option to tell her you were sent by Dr. Hildern with the same effect.
Oh, you can then report back to him in order to complete his quest and that will not interfere with
Veronica's own quest.


Good luck

Thanks. Can you get to that pulse gun without Veronicas quest being active at that point?

Yes, absolutely. The Pulse Gun will be there after Veronica's quest is completed just
as it is there before, even when Veronica isn't your companion (I got it much earlier and
I was with Cass at the time). Hint: having the Pulse Gun before ending
Veronica's quest is rather helpful...