How is the new anti-conversion law going to affect Christians in India? There is news that Modi government likely to bring bill to prevent religious conversion in next Parliament session
There is currently this plea from persecution relief and a petition to be signed
How have such laws affected Christians in the world in the past?
And how would they affect Christians in India?
Have such laws caused any type of unity and revival of fellowship among denominations who would not otherwise fellowship with each other in the past in world history?
There's many a slip twixt cup and lip, so until an actual law is actually passed, we can only surmise. The history tag is useful to remind us that in every generation, sections of Christians in different parts of the world have had legislation enacted against them to stop their God-given commission to share the good news about Jesus everywhere. Many vicious tactics have been employed against the liberty of Christians to share the gospel with other. Yet there really is only one answer to your complex question, and it has little to do with what modern-day governments in India might do in the very near future.
You ask, &quot;How would [such proposed laws] affect Christians in India?&quot; As history shows, Christians will be scattered, blood will be spilled, and many people will be converted to Christ by the power of the Holy Spirit, through such adverse circumstances. As the North African Christian theologian Tertullian (circa 155-220A.D.) wrote,

&quot;The blood of the Christians is the seed of the church&quot; (chapter 50 of
his Apology.) [See this, Henry Bettenson's correct quote, Doctrines of the Christian Church page v.]

In other words, the more the Romans persecuted and killed Christians, the more the church grew.
Government laws to try to stop Christians encouraging people to turn in faith to Christ are counterproductive. That is because conversion to Christ is the work of the Holy Spirit, not of individual or collective Christian efforts at evangelism. Non-Christian governments always misunderstand this and think that by proscribing evangelism, conversions will more or less stop. What happens is that Christians go &quot;underground&quot; (as in China) with antagonistic groups grasping the legislative opportunity to turn on Christians, to betray them to the authorities, or to invent lies with which to get them accused in courts. Yet people are still converted to Christ! Baptisms keep happening. The faith of the faithful keeps growing. Yes, many professed Christians may fall away, but that does not stop conversions to Christ continuing. Why? Because that is the role of the Holy Spirit. He convicts people of their sin, giving them such a burden of sin that they cry out to God in repentance, to be forgiven. When they are freely forgiven by God, they are converted and become Christians.
No laws passed by any government has ever been able to stop this. But because ungodly governments know nothing of the things of God and of the way the Holy Spirit operates, they keep trying to suppress the Church visible, thinking they are succeeding when, hidden in plain spiritual sight are increasing conversions enacted by the Holy Spirit.
Yes, Christians undergoing such duress will find spiritual encouragement and help from those they might not normally fellowship with. This is another evidence of the Holy Spirit at work, building up the body of Christ where secular powers have tried to break it down. Despite some falling away from the faith, others remain faithful to Christ. Denominational 'identities' are seen to less important than previously supposed, under dire circumstances of persecution. Which is what anti-conversion laws designed to silence Christian witness and testimony actually is. It may be couched in apparently sensitive language, to allow for 'legitimate' or 'genuine' conversions that can be shown to be un-forced, but recent history shows many non-Christians accusing Christians of trying to bribe people into conversion when they were only helping the starving to get some food or shelter. That sort of thing.
Nobody can prognosticate and give you a precise answer as to how such proposed laws might affect Christians in India, so my answer is speaking in broadly general terms, based on what has happened to Christians in different parts of the world, at different times. Jesus promised that the Church he builds will not be overcome, not even by the gates of Hades. Those individuals who make up that spiritual 'body of Christ' will stand firm and continue to point others to Christ, by word and by deed, and the Holy Spirit will continue to do his work of conversion.