Sorry, this is so long....I'll break it up. So many good questions....
I understand but people who practice tongues and spiritual gifts are deceived?
I believe that because the Bible warns that those who present "powerful works" or "signs and wonders" (once the "weeds" had taken over Christianity as Jesus foretold) are deceived by the devil, so we should be alert. If these occurred after the apostolic period was over, it would be the works of the deceiver.
Think about how logical that is. The gifts and miracles were used to draw unbelievers to Christ in the first century, but once the congregations began to flourish, and the apostles had penned their contribution to scripture, the gifts were no longer necessary. "Faith. hope and love" would now suffice.
If the devil was going to set up a counterfeit system with his own tricks to draw the unwary, then instead of wondering who are genuine ones and who are not, the proof that it is genuine has nothing to do with half-baked miracles. The devil is just a mimic.
What was to identify true Christianity was "love amongst themselves". (John 13:34-35) Christendom's fragmented condition is not God's doing. (1 Corinthians 1:10) It is the work of the deceiver.
But if you knew He existed then there wouldn't be a need for faith, faith is usually required in the absence of knowledge.
Have you seen Paul's definition of faith?
Hebrews 11:1...."Faith is the assured expectation of what is hoped for, the evident demonstration of realities that are not seen."
Faith is strengthened by "knowing" that he exists. He is the 'reality, that is not seen'. Our expectations are not empty pipe dreams...they are "assured".
If a person has never had a personal relationship with God; never having him participate in their lives in amazing (though not miraculous) ways, it's hard to explain. But the more you put your life in his hands and follow his advice and laws, the more you experience the reality of him.
But if we're incentive oriented doesn't that mean that we're doing it out if selfishness and self interest and if God's rewards are the main motivator for a relationship with Him doesn't that make it fake and shallow rather than real since we don't really love Him for who He is but what He can do for us?
There is line where, if it is crossed, puts us exactly there. We have to have the right motivation. It's not wrong to look forward to the reward, but if our prime motivation is not love for our Father, then as a reader of hearts, he knows. Sometimes we don't, but a test will reveal how strong our faith really is. If we cave at being tested, then we never had God in the first place.
To illustrate, Jesus gave a parable on the different "soils" (hearts) where the seed of truth is planted. (Matthew 13:3-9)
Some seed fell along the roadside where birds came and ate them. (People who have a heart that is not fit to plant the seed in, so the message goes in one ear and out the other)
Some seed fell on rocky soil with no depth. The seed sprouted but because the soil was shallow, there was no room for further growth. (People who get excited about the promises of the kingdom, but discover that it requires something of them, that they are not prepared to give. The road to life is not easy and involves hardship. They want the reward but are not prepared to endure the inevitable tests that the devil will bring.)
Some fell among the thorns, which grew up and choked the seedlings because they were competing for space. (These would also involve the very personal hardships that becoming a Christian can bring, such as persecution or strong opposition brought to bear by family, friends or even governments. (Matthew 10:34-36; Ephesians 6:10-13)
But there was fine soil where the seed sprouted and had space to put down roots and no matter what hardship was brought to bear, they survived to become full grown....strong and healthy.
We all fall into one of those categories. Where would you place yourself?