6. If you are still using a legacy addresses, use a wallet that supports (wrapped Segwit) 3 or BC1 (native Segwit). send when the network is not congested.
The nested segwit (compatible bitcoin addresses) start from 3, but the native segwit start with bc1 not BC1.
8. If your wallet does not support RBF CPFP, it is best to stop using it.
Noncustodial sender wallets supposed to be able to use CPFP (if you are the sender), it is different from RBF. While the recipient wallet will need to be able to spend unconfirmed transaction before it can be able to use CBFP. Few wallets like electrum and Bitcoin core can make use of RBF.
12. Remember what the transaction has not been confirmed and it is in yours. Therefore, if someone sends the money to you and it is not confirmed in the sender’s wallet.
Yes, because unconfirmed transactions can be reversed.
15. Fees are necessary to ensure network decentralization, but knowing how that system works will make you pay cheaper
The fee charged works in a decentralized manner but does not ensure decentralization. What ensure decentralization is that anyone with miners can mine and pick up transactions according to mempool size, mining is not centralized in any form truly. So, just know that mining itself is decentralized.
Fees are calculated in satoshi/vbytes. Johoe's Bitcoin Mempool Statistics, you can interpret it like this:
The data is separated into different fee levels given in satoshi per bytes. The lowest colored stripe is for transactions that pay the lowest fee. Higher fee transactions are stacked on top of it. Since miners prefer high fee transactions, a new block usually only removes the top 1 MB from the queue. If a colored stripe persists over several hours without getting smaller, this means that transactions paying this amount of fee are not confirmed during this time, because there are higher paying transactions that take precedence. If a stripe on the bottom chart is much bigger than on the top chart, the transactions are larger than the average.
So, the upper part of the graph with 1 MB are only taken by miners in accordance to the mempool congestion. Low fee transactions may not be taken up if the mempool is congested. The 1 MB transaction size that will be taken up by miner are the transactions above while the ones below in blue and green colour will not be taken up until mempool is not congested, and at the time of mempool not congested, the part that are green will become yellow (up part) while the blue parts will reduce while the upper blue parts will turn green. I hope this will make you understand.
There is another way to pay cheaper fees without looking at mempool, so what is it?
Wallets have fee estimator, but some may not be accurate. You can use electrum and I have used mycelium before, they have good fee estimators. Any wallet you are using, you can compare the fee estimation with the ones online to know the accuracy of the fee estimated. The fee estimators are discussed below.
There are several online fee estimators that can determine fee to be paid. These are some:
https://bitcoinfees.net/https://mempool.space/https://bitcoinfees.earn.com/https://privacypros.io/tools/bitcoin-fee-estimator/https://mempool.observer/Why are some transactions dropped or returned after 14 days? What is the shortest period for that?
That is how the mempool work, any transaction that is not confirmed for 2 weeks will be dropped and the Bitcoin amount will be refelcted back on the wallet balance. It is better like that than for transaction to be stuck in mempool longer.
What is the difference between (native Segwit) and (wrapped Segwit)
Native SegWit – also known as bech32 – is the latest step in the address formats. It is even more weight-efficient than its predecessor. This means having an even faster transaction speed versus SegWit transactions, better scalability and even lower fees per transaction. To add to this, bech32 has better error-detection and makes addresses lowercase only for better readability. This is why it’s the most popular option… if present.
Is there one mempool or several mempools and what is the difference between them?
There is only one mempool available to all.Each node has its own mempool, which is why transactions need to be relayed across the network from node to node and added to each mempool as they go. Some nodes may set different size limits for their mempools, or different minimum fees that they will accept before adding a transaction to their mempool. A transaction can be present in some mempools but not others.
Can the transaction fee be adjusted while keeping the same tx id?
No. Using RBF simply means your initial transaction will be cancelled while another address will be used to transfer the Bitcoin fund into the same recipient/receiver's address, this will generate a new txid.
Why does the wallet hide your wallet balance during the confirmation?
That is how wallets are programmed, if the transaction is in mempool, it will leave your wallet balance, if not confirmed, it can still be canceled and be seen back on your wallet balance. Electrum wallet have this feature, which is a means of using RBF to send unconfirmed bitcoin into another address generated by your wallet in which new txid will also be generated. Or, if the transaction by any means leave the mempool, it will be back into your wallet and your balance will reflect it.
After broadcasting, Can an address be modified without changing a tx id?
No, address can not be changed after broadcasting, any modifications will lead to changed address and new txid as explained above.
Can two blocks be mined almost simultaneously? Does that mean that if we send two transactions with the same inputs but different outputs, we will succeed in double spending?
I only know that two blocks can be mined simultaneously, or two mining pool can mine the same block at the a time. This can lead to a transaction to be confirmed but later be invalidated because only the longest chain will only be successful and validated. This can also happen if someone use RBF in which the first transaction that supposed not to be confirmed will be confirmed while the second transaction too will be confirmed. But finally, the first transaction that was confirmed will later be invalidated. Nothing of such like double spending.
