Why is Nepal called a three-tier federation?

Features:1. Dual executive: a ceremonial head of state (monarch/president) + a head of government (Prime Minister) holding real power;2. Fusion of powers: ministers are (or quickly become) members of the legislature;3. Collective responsibility: the Council of Ministers is jointly responsible to the legislature (in Nepal — to the House of Representatives);4. Survival by confidence: the government falls if it loses the House's confidence; conversely the executive may seek dissolution and a fresh mandate;5. No fixed tenure: the government lasts only as long as majority support;6. Leadership of the majority party — the PM is normally the majority leader.Merits: harmony between executive and legislature; flexibility (change of government without election); accountable daily (question time); trained leadership. Demerits: instability (coalition churn); executive dominance of the legislature when majority is solid ("elective dictatorship" — Hailsham); divided accountability in coalitions; cabinet secrecy.