for #1 : no they cant force u to get ur car fixed at another guarage because u said its 3 months old.. ( as long as its brand new- bought in the same year) so u r definitely fixing it at "nissan's"
for #2 : no man! its not their fault that ur car got hit.. so u probably will hire on ur own and pay for it urself ;)
for #3: i see no question :)
hope this helps!
,
Emad =>