The Bible clearly teaches about dispensations!

Dispensation, or Administration are periods of time that start with God’s dealing with men in a favorable circumstances, with a particular test, and ends in failure and judgment. 
What God said during one dispensation may or may not be applied to another. 
This will help answer a lot of your questions. Right now I suggest you focus on getting to know God in the New Testament. For all that is written in the New Testament applies to us living right now, in this the present dispensation of Grace. 

1. Dispensation of Innocence: From creation of Adam and Eve created sinless, to when they sinned and were expulsed from the Garden of Eden. Did not last long I would give it less than a week!

2. Dispensation of Conscience: From the expulsion from the Garden of Eden to the flood of Noah. Lasted 1,656 years. 

3. Dispensation of Human Government: From the flood of Noah, to the call of Abraham. Lasted 427 years. 

4. Dispensation of Promise: From the call of Abraham, to the exodus of Israel from Egypt. Lasted 430 years. 

5. Dispensation of Law: From the exodus of Israel from Egypt, to the preaching of John the Baptist, or from Moses, to Jesus’ first coming. Lasted 1,718 years. 

6. Dispensation of Grace: From Jesus’ first coming, to Jesus’ second coming. Lasted so far over 2,000 years. 

7. Dispensation of Divine Government – The Millennium: This age will start when Jesus comes back to set up the Kingdom of Heaven on Earth: It will last 1000 years. 

8. Dispensation of the Redeemed and faithful Angels: After the 1000 years, all sin will be purged, and God will then move His capital from the planet Heaven, to the planet Earth. The Kingdom of Heaven, will give way to the Kingdom of God!