The kingdom of heaven is like the grain of mustard seed and like the leaven that goes through the whole lump; both analogies show that the kingdom grows from small beginnings before it can be known. Mark further reports:
And he said, To what shall we liken to the kingdom of God? Or with what parable shall we picture it? It is like a grain of mustard seed, which, when it is sown in the earth, is less than all the seeds that are in the earth. But when it is sown, it grows up, and becomes greater than all herbs, and shoots out great branches; so that the fowls of the air may lodge under the shadow of it. Mark 4:30-32
So, in the beginning of your seeking the kingdom within, it is smaller than the tares of the world, which are the lusts, pride, worries, cares, and pleasures. But if the seed of God's kingdom is watered and fed, it grows to be the largest of all; this seed is watered and fed through seeking the Lord, through silent waiting for him, listening for his voice, hearing his teachings and commands, and obeying them as directed from God.
2 Regarding the end of the world: Mat 28:20 states, I am with you always, even unto the end of the world. The disciples are not still alive on the earth waiting on the end of the world. This statement makes no sense, unless you realize the end of the world is a personal experience — as it was for the disciples — for they saw the end of the world. And the world passes away and disappears, and with it the forbidden cravings (the passionate desires, the lust) of it; but he who does the will of God and carries out His purposes in his life abides (remains) forever. 1 John 2:17. So the world with its lusts and passions disappear together, crucified by the aid of the Spirit. After we are purified, Christ returns to establish his Kingdom within us, and the world as we know it disappears. We enter a different dimension - paradise or the Kingdom of Heaven. Now all these things happened unto them for examples; and they are written for our admonition, upon whom the ends of the world have come. 1 Cor 10:11.
The world ends as you step into a different parallel dimension, the Kingdom of God that is within and around us - it is a different dimension to be lived in, a spiritual dimension to be entered through personal tribulations while still physically on the earth; and then to dwell there forever. But, unless you enter the Kingdom of Heaven in this life, you will never have any inheritance in the Kingdom of Christ or God. The Books of Acts and Ephesians helps us understand the Kingdom of God within and among us: God .. is not far from each one of us, for in him we live and move and have our being, Acts 17:27-28, and One God and Father of all, who is above all, and through all, and in you all. Eph 4:6- but we are not aware of this because we are in a lower physical dimension. The physical dimension shares the same space as the higher spiritual dimensions; one God and Father of all, who is over all and through all and in all. Eph 4:6. To enter the Kingdom of God within and around us, is to be dramatically translated to the spiritual dimension of consciousness and sight, in union with Christ and God, but walking on earth by the light of God. The world passes away from our sight when the Kingdom is entered.
3 If you die in your sins, you are going to be banned from heaven:
The acts of the sinful nature include adultery, fornication, uncleanness, lewdness, idolatry, sorcery, hatred, contentions, jealousies, outbursts of wrath, selfish ambitions, dissensions, heresies, envy, murders, drunkenness, revelries, and the like, etc.
...those who do such things will not inherit the kingdom of God. Gal 5:19-21
All with sexual immorality, pride, hatred, lying, envy, wanting more, partying, foolishness ..etc., will be banned from heaven.
You can be sure: No immoral, impure or greedy person..has any inheritance in the kingdom of Christ and of God.
Let no one deceive you with empty words, for because of such things God's wrath comes on those who are disobedient. Eph 5:5-6
Anyone who is impure, immoral, or greedy will be banned from heaven.
Jesus said,.. For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, thefts, covetousness, wickedness, deceit, lewdness, an evil eye, blasphemy, pride, foolishness. All these evil things come from within and defile a man. Mark 7:21-23
Notice, until your heart has been cleansed, you are defiled - a ravenous beast that serves yourself, rather than others.