Solution
Neighbours to label: Pakistan, Afghanistan (land border in PoK), China, Nepal, Bhutan, Bangladesh, Myanmar (land neighbours); Sri Lanka and the Maldives (maritime neighbours).
Cultural flows (arrows): Buddhism from India to Sri Lanka, Myanmar, Bhutan and Nepal; food like biryani, momos (Nepal, Bhutan, Tibet) and Bengali sweets moving both ways; languages (Bengali, Punjabi, Tamil, Nepali) shared across borders; festivals like Diwali/Tihar, Eid, Vesak and the Bengali New Year.
Borders of friendship: draw zones along shared rivers (the Ganga–Padma, Brahmaputra, Indus), old trade routes (the Grand Trunk Road, the Silk Route) and cultural zones (Bengal, Punjab, the Himalayan Buddhist belt).
Flags (sample observations): Bhutan's flag has a dragon; Nepal's is the only non-rectangular flag (two triangles); Sri Lanka's shows a lion with a sword; Bangladesh's has a red disc on green; many use green (Islam or nature), saffron (Hinduism or Buddhism) and the sun or moon.
Label all land and maritime neighbours, draw arrows for Buddhism, food, languages and festivals, sketch friendship zones along rivers, trade routes and cultural regions, and note flag features (Bhutan's dragon, Nepal's triangles, Sri Lanka's lion).