Qn 1. How do we know for certain the call of God ?

Though God’s call to salvation is Universal
( Acts 17 : 30 ), only those appointed to eternal life will respond to it. ( Acts 13 : 48 ) That is in agreement with what we read in Scripture : “For those God foreknew, he ALSO predestined; those he predestined, he ALSO called; those he called, he ALSO justified; those he justified, he ALSO glorified.’ ( Ro 8:30 )
The word ‘ALSO’ guarantees us that , ‘He who began a good work in you will carry it on to completion until the day of Jesus Christ.‘ ( Phil 1 : 6 )
Though all who are saved are entrusted with the ministry of reconciliation ( 2Co 5 : 18 – 20 ), God calls some to the fivefold ministry.
It was he who gave some to be Apostles, some to be Prophets, some to be Evangelists, and some to be Pastors and Teachers, to prepare God’s people for works of service. …’ ( Eph 4 : 11, 12 )

Jesus went up on a mountainside and called to him those he wanted and they came to him. He appointed the twelve – designating them Apostles’ ( Mark 3 : 13, 14 )
Not that there were no other capable men among those that followed him, ‘But God chose the foolish to shame the wise; the weak shame the strong; the poor to shame the rich so that no one may boast before him.’ (1 Co 1 : 27, 28 )
They heeded to the unmistakable call of Jesus. They left everything to follow him ‘for it was God who worked in them to will and to act according to his good purpose.’ ( Phil 2 : 13 ) Often we wish that Jesus would call us thus and indeed he is calling us by his Holy Spirit.
If you have a calling on your life, be certain that the Spirit of the Lord will begin to stir you as he did Samson (Judges 13 : 25 ) It is an unmistakable unction that you feel within, which you know for certain is God. It doesn’t require much knowledge of Scripture to figure it out. If somebody is struggling will it, it is because they are fighting against it. Yield to it and then it becomes the only thing left for you to do.
I consider my life worth nothing to me, if only I may finish the race and complete the task the Lord Jesus has given me – the task of testifying to the gospel of God’s grace.” (Acts 20 : 24 ) Amen.