Yes, they are very close and often interchangeable in everyday conversation. However, saying into can help clarify in some cases.

In is a preposition that tells you an action is happening from the inside of something.

Into means there is a movement from the outside to the inside.

They walked in the house. (They were in the house and were walking around OR They walked in from outside)

They walked into the house. (They walked from the outside to the inside)

He jumped in the lake. (He was in the lake when he jumped OR he was at the edge of the lake and jumped into it)

He jumped into the lake. (He jumped from outside the lake to the inside…and got wet)

Upon and on are interchangeable. If you want to sound more educated, say on. If you want to sound more natural, say on. Your choice.