No verse claims Cain had to work the ground outside of Paradise.
"If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him."
God was warning Cain not to let sin into Paradise.
No verse claims that Cain worked the ground inside of paradise. Working the ground was a curse given when they were cast out.
Genesis 3:17-20
17 To Adam he said, “Because you listened to your wife and ate fruit from the tree about which I commanded you, ‘You must not eat from it,’
“Cursed is the ground because of you;
through painful toil you will eat food from it
all the days of your life.
18 It will produce thorns and thistles for you,
and you will eat the plants of the field.
19 By the sweat of your brow
you will eat your food
until you return to the ground,
since from it you were taken;
for dust you are
and to dust you will return.”
20 Adam named his wife Eve, because she would become the mother of all the living.
Notice that Adam named Eve after this before she gave birth.
Genesis 4:4-16
4 Adam made love to his wife Eve, and she became pregnant and gave birth to Cain. She said, “With the help of the Lord I have brought forth a man.” 2 Later she gave birth to his brother Abel.
Now Abel kept flocks, and Cain worked the soil. 3 In the course of time Cain brought some of the fruits of the soil as an offering to the Lord. 4 And Abel also brought an offering—fat portions from some of the firstborn of his flock. The Lordlooked with favor on Abel and his offering, 5 but on Cain and his offering he did not look with favor. So Cain was very angry, and his face was downcast.
6 Then the Lord said to Cain, “Why are you angry? Why is your face downcast? 7 If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must rule over it.”
8 Now Cain said to his brother Abel, “Let’s go out to the field.” While they were in the field, Cain attacked his brother Abel and killed him.
9 Then the Lord said to Cain, “Where is your brother Abel?”
“I don’t know,” he replied. “Am I my brother’s keeper?”
10 The Lord said, “What have you done? Listen! Your brother’s blood cries out to me from the ground. 11 Now you are under a curse and driven from the ground, which opened its mouth to receive your brother’s blood from your hand. 12 When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth.”
13 Cain said to the Lord, “My punishment is more than I can bear. 14 Today you are driving me from the land, and I will be hidden from your presence; I will be a restless wanderer on the earth, and whoever finds me will kill me.”
15 But the Lord said to him, “Not so; anyone who kills Cain will suffer vengeance seven times over.” Then the Lord put a mark on Cain so that no one who found him would kill him. 16 So Cain went out from the Lord’s presence and lived in the land of Nod, east of Eden.
Again no verse mentions that Cain was in the garden as the text says he was born after Adam and Eve were cast out on the garden. Also notice that there is no cherub mentioned gaurding the gate in Cains story