Nepali

Both Indo-Aryan, related but distinct. Nepali and Hindi share grammatical structure, postpositions, SOV order, gender agreement, and split-ergative past, plus many cognates and Sanskrit-derived vocabulary. Speakers of one can often follow basic conversation in the other, especially in writing. But verb conjugations, pronouns, and many everyday words differ enough that fluency in one doesn't fully transfer to the other.

Nepal as the official national language, with around 13 million native speakers in the country (where Nepali is also a second language for many speakers of other languages). Indian states with substantial Nepali populations include Sikkim (where Nepali is co-official), West Bengal (Darjeeling), Assam, Manipur, and Uttarakhand. Bhutan has a Lhotshampa Nepali-speaking minority. Nepali diaspora populations exist in the Gulf, the United States, the United Kingdom, and Australia.

Yes — three honorific levels for second-person pronouns and verb forms, ranging from very informal (timi) to neutral-respectful (tapai) to highly respectful (yahā or hajur for elders and high-status addressees). Verb endings shift accordingly. The system is similar in structure to Hindi's but uses different surface forms. Choosing the wrong honorific level for the listener is socially marked.

No — Nepali is Indo-Aryan (Indo-European), Tibetan is Tibeto-Burman (Sino-Tibetan). Nepal is geographically squeezed between the Indo-Aryan and Tibeto-Burman language zones, and Nepali has absorbed Tibeto-Burman vocabulary through long contact, especially in highland regions. Many Nepalis are bilingual in Nepali and a Tibeto-Burman language (Tamang, Magar, Newar, Sherpa, Limbu, etc.) that they speak at home.

About on par with Hindi in difficulty — Devanagari script (a few weeks), Indo-Aryan grammar with postpositions, SOV order, gender agreement, and split-ergative past. The honorific system adds complexity. Vocabulary is heavily Sanskritic with Tibeto-Burman loans and increasing English borrowing in urban speech. Most learners reach reading literacy faster than fluent conversation.