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

The union leader's proposals could not be accepted by manager.

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

Rule :
Subject + Model verb +not + be + V3 + Optional Objects.

English is spoken all over world.

Given sentence is in Present simple tense.

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

Let this be done by me.

If a sentence is started with Let passive voice of that sentence also be started with Let.

Rule :
Let +Subject +be + V³ + Or agents.

He was given a reward by king.

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.

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 prices were lowered by shopkeeper.

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.

The landscape is dotted by tiny houses.

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

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

They will not be allowed to run away by us.

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

Where are current magazines kept by you?

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

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