No, it's not possible yet on Duolingo.
Yes except no-one but the prissiest of the prissiest would say see-NEET (I’m pretty sure it’s not even prescriptively correct). It’s SEE-neet.
They have many problems with pronounciations. Chemistry for example, they pronounce kimia and not khimiya, which is erong since that word is not a Hebrew word so beged kefet doesn't apply to it.
It’s a loanword. Beged kefet does not apply to loanwords.
Are there other language names that get penultimate stress?
לא, אני למדת עברית.