Cricket was being played by boys.

Given sentence is in past continuous tense and it is in active voice.

Rule :
Subject + (was/were) + being + V³ + Or agents

All details of invention have been published by m.

The given sentence is in active voice and it is in Present Perfect Tense.

Rule :
Subject + (has /have) + been + V³ + Or agents.

Men, women and children throng shops before festival making various purchases.

Given sentence is in Passive voice and in Present Simple Tense. We need to change it into active voice. While changing voice objects becomes subject and subject changes into object.

Rule :
Subject + V¹ + Or agents.

A fox was caught by tiger.

Given sentence is in Past simple tense and it is in active voice, we need to change it into passive voice.

Rule :
Subject + (was / were) + V³ + Optional Agents.

We gave our colleague a gift when she retired.

Given sentence is in Past simple tense and it is in Passive voice, we need to change it into active voice.

Rule :
Subject +V² + Optional Agents.

Cats are always chased by dogs.

Given sentence is in simple present tense and it is in active voice.

Rule :
Subject + (is/am/are) + V³ + Or agents

The elders must be respected.

The given sentence contains one of Model verb (Model Verb = will, shall, can, may, might, could, might, must, would). It is in active voice.

Rule :
Subject + Model verb + be + V3 + Optional Objects.

Why wasn't matter brought to my notice?

Given sentence is in simple past tense and it is in active voice.

Rule :
Why + (was/were) + Subject + V³ + Or agents

Happiness is given by God.

Given sentence is in simple present tense and it is in active voice.

Rule :
Subject + (is/am/are) + V³ + Or agents

Given sentence is in present simple tense and its passive would be:
A letter is written by Rajat.