Sindhi

Implosives are made by lowering the larynx during a voiced stop, creating an inward suction that gives a hollow, popping quality compared to ordinary voiced stops. Sindhi has four phonemic implosives — ɓ, ɗ, ʄ, ɠ — each contrasting with the corresponding plain voiced stop. Implosives appear elsewhere in the world (West African Igbo, Hausa) but are rare in Indo-European languages, making Sindhi a notable exception.

In Pakistan, a modified Perso-Arabic script with extra letters added for Sindhi-specific sounds (including the implosives). In India, both Perso-Arabic and Devanagari are official, with Devanagari more common in younger Indian Sindhi publishing and Perso-Arabic preserved in older Sindhi-Hindu literary traditions. Some Sindhi communities use the Khudabadi (or Khojki) script for community-specific religious and merchant contexts.

Mostly in the Sindh province of Pakistan (around 23 million speakers, the dominant regional language). Indian Sindhi communities — descended from Hindu Sindhis who migrated during Partition — are found across Mumbai, Gujarat, Rajasthan, and the diaspora. Sindhi is also one of the 22 scheduled languages of India. Diaspora Sindhi communities live in the United Kingdom, the United States, Hong Kong, and Singapore.

Yes, two: masculine and feminine. Verbs, adjectives, and some postpositions agree with the noun. Like Hindi, Marathi, and Punjabi, Sindhi has a split-ergative past tense — in past transitive sentences, the verb agrees with the object and the subject takes a special case marker. Sindhi grammar in this respect resembles its Indo-Aryan neighbours, just with a notably different phonological system.

No — both Indo-Aryan, but distinct languages. Sindhi and Punjabi are spoken in adjacent regions of Pakistan, share grammatical structure, and have many cognates, but they're not mutually intelligible without exposure. Sindhi has implosives Punjabi lacks; Punjabi has tones Sindhi lacks; the verb conjugations and many basic words differ noticeably.