questions about bitcoin

I have few questions..

1. There is a cycle of 4 years with the halving and all. But what if, if all countries adopt it, there will be never a new low right?

2. What is the difference between pay with bitcoin and pay with your debit card?

3. If you do a payment and there are very much payments you come in the memepool ( waitingroom ) so how is this gonna work if its a world currency?

4. And last but not least, what must we do with bitcoin because if we hodl it, it becomes a value thing like gold. But if you spend it they accept it more in the society so both things are good. But if we want that it becomes a currency than we must spend it right? Or do we want it as a store of value?

Just curious.. thanks 🙂