Re: Biellette -- the impression I get from Luc's and André's explanation is that it's a word for "torque tube" or possibly "control rod." The impression from context in the accident is that the biellettes in the first machine built by the mishap pilot reinforced the mast in some way.
Re: stick movement. The impression I get is that the mast swung around at the juncture between upper and lower parts due to asymmetry created by the bird strike. (Whether the report means, asymmetry of lift, or of mass, is not clear, but probably lift). And the pilot was not able to damp this movement out with the control stick.
FWIW the BEA website does not seem to contain this accident at first glance. 2000 is not an option when selecting "year" -- if you search "all" years and select "autogire" as class of aircraft, you get ten mishaps which don't seem to include this one.
The BEA website is in French, English and Spanish so almost everybody can read in his native language (sorry, Rehan... no Urdu!). But the accident reports may only be in French.
https://www.bea-fr.org/
I guess my teachers were right in junior high school: "Someday you will need to understand French and you will thank me for this, even though you curse me now, ungrateful child!"
cheers
-=K=-