Explanation:

Part XVI deals with reservation of SC and ST in Central and State legislatures. 

• Article 15(4) and 16(4) of the Constitution enabled the State and Central Governments to reserve seats in government services for the members of the SC and ST.

The Constitution was amended by the Constitution (77th Amendment) Act, 1995 and a new clause (4A) was inserted in Article 16 to enable the government to provide reservation in promotion.

• Later, clause (4A) was modified by the Constitution (85th Amendment) Act, 2001 to provide consequential seniority to SC and ST candidates promoted by giving reservation.
• Article 330 and 332 provides for specific representation through reservation of seats for SCs and STs in the Parliament and in the State Legislative Assemblies respectively.
• Article 243D provides reservation of seats for SCs and STs in every Panchayat.
• Article 233T provides reservation of seats for SCs and STs in every Municipality. 
• Article 335 of the constitution says that the claims of STs and STs shall be taken into consideration constituently with the maintenance of efficacy of the administration.
• The 103rd Constitution Amendment Act, 2019, empowered both Centre and the states to provide 10% reservation to the EWS (Economically Weaker Section) category of society in government jobs and education institutions.

Hence only statement 1st is correct.