None of the statements are correct for the following reasons:

1. Election Void Effect: If the election of the President of India is declared void by the Supreme Court, the acts performed by the President before the ruling do not automatically become invalid, as decisions made before a judicial verdict typically remain effective until overturned.

2. Postponement of Elections: The Constitution does not provide for postponing the presidential elections based solely on the dissolution of Legislative Assemblies; such elections are governed by the Election Commission's authority, which acts independently to ensure timely conduct.

3. Time Limits for Presidential Assent: While there are provisions regarding the time frame within which the President must act on a bill (like returning it for reconsideration), there is no strict constitutional deadline for giving assent or withholding it, leading to uncertainty about the specifics of any prescribed limits.

These misconceptions highlight the complexity of electoral laws and constitutional provisions in India, which are crucial for understanding governance and legislative procedures, a key topic in UPSC Civil Services Examination syllabus.