Some Bitcoin Questions

Hello guys,

I have some quesions regarding the Bitcoin Basic course, hope someone can help me with that.

Lecture Transactions, UTXOs & Fees

  • I understood that there is rule that a transaction has to spend all inputs. Does this mean that if I have received 3 BTC during the course of last month and I will send 1 BTC to a friends address actually all my 3 BTC are send, 1 BTC to address of the friend and 2 BTC back to me, meaning to the sender address?

Lecture Mempool:

  • I understood that transactions that are more complex (several inputs & outputs) are large in size (bytes) and thus the fee is higher meaning that the miner earns more. This means that a miner is inclined to put transaction thats are more complex in his block, is this correct?

Lecture Block Rewards & Halvenings:

  • It is said that tx fees increase because more people are using bitcoin. I do not understand this, why should tx fees increase as more people use bitcoin?

Lecture Orphaned Blocks:

  • What happens with the rewards the miner received after the block is removed and the transactions go back into the mempool?
  • Best Practice is to wait 6 confirmations, meaning for 6 additional blocks, this means that only after around 1 h you can be sure that your transactions will not be dropped because it might be in an orphaned block, right?
  • How common is it that orphaned blocks occur? Does this happen often?

Thanks a lot for your help