The winning percentage varies by crypto. When staking, the rate will appear in %. The amount of coins does not change.

1 - Does anyone know what this flexible deposit percentage is for Simple Earn?

From what I understand, it is an amount lent to traders and returned as a percentage.

2 - How many days does it need to remain invested for the APR to return?

3 - What is APR?

4 - Is there a risk of losing the money invested in this Simple Earn because it is lent to other traders, or does Binance have a control and limit so that it is not lost?