Take note that your wallet file includes all the private keys and anyone who has access to the file and know the passphrase (if there's any) can steal your bitcoin. (The passphrase can be brute-forced, if it's not strong enough.)
Share the wallet file if you are sure that the person is trustworthy enough and ignore personal messages you will probably receive.

The block time has nothing to do what's going on in the mempool.
Miners solve the proof of work problem to mine a block and the time the problem takes to be solved doesn't depend on the number of transactions in the mempool and the fee paid for them.

There is no exact number.
As already mentioned, difficulty changes every 2016 blocks, so the average block time stay close to 10 minutes.
If the average block time is more than 10 minutes, the problem becomes easier and if the average block is less than 10 minutes, the problem becomes more difficult.  


That's not possible.
Each private key provides 128 bits of entropy.  

No.
For mining a block, miners need to solve a mathematical problem which is called proof-of work problem.
This problem is solved through brute-force method. This means that the problem is solved by checking all possible answers. It's possible that the problem is solved in a few seconds. It's also possible that it takes more than an hour until a miner finds the solution.

First of all note that it's unlikely that you have an output of 280 satoshi in your address. Because that's smaller than the dust limit.
Anyways, there is no problem with transaction fee of 140 satoshi if the fee rate isn't lower than 1 sat/vbyte.
The problem is with the value of your output which is lower than the dust limit.

Your transaction should meet following requirements:
1. The fee rate should be at least 1 sat/vbyte.
2. The outputs you create should be bigger than the dust limit. (Dust limit is 294 satoshi if the address is segwit and 546 satoshi if the address is legacy.)


Whether you have 300 satoshi or 280 satoshi, you can't make the transaction.
If you have 300 satoshi and you create an output with the value of 294 satoshi, you can't pay the transaction fee. The remaining 6 satoshi isn't enough for the transaction fee.
Assuming the transaction is 140 vbyte and you set the fee to 1 sat/vbyte, you need to pay 140 satoshi for the transaction fee.

This is wrong.
It's possible to make a transaction with lower fee.
A segwit transaction with 1 input and 1 output has a virtual size of around 140 vbytes. If you set the fee to 1 sat/vbyte, the fee would be only 140 satoshi.

Note that dust limit is the minimum value of an output you can create and that has nothing to do with transaction fee.
For a legacy output, the dust limit is 546 satoshi and for a segwit output, the dust limit is 294 satoshi.

Yes, they do.
They show the 12 words in incorrect order and you have to put them in the correct order to create the wallet. They also display a warning about importance of keeping the seed phrase.

Right.
All your keys (private keys, public keys, addresses) can be derived from your seed phrase (a series of 12 words).
In the case you lose your phone for any reason, you can import your seed phrase into a new wallet and access your fund.

Trustwallet is close-source and there is no way to know how keys are generated and whether they are stored in their server or not.

Your seed phrase is all you need for backing up your wallet.

Take note that with using legacy addresses, you have to pay more transaction fee and it's always recommended to use segwit addresses.
I recommend you to try to solve the problem with mycelium and use segwit addresses.
The problem should be solved with updating mycelium to the latest version.

Coinomi allows you to sign message from legacy and native segwit addresses.

As there is no standard algorithm for signing message from segwit addresses, it's worth mentioning messages signed by coinomi from that type of addresses are verifiable by electrum.
Also note that coinomi is close-source.  

Most probably, the accounts have been deleted due to abusing the website.

Not quite true.

Assume that you made 1 post in the first two-week activity period and 1 post in the second two-week activity period and now you are in the third period.
In the third activity period, you can make 40 posts and get 40 activity.

You can enter your address(es) in a block explorer like blockchair and check your balance.
For spending your bitcoin, you can export your private key(s) and import them into a SPV wallet like electrum.

Did you delete the "databases" folder or you just updated Armory and didn't delete that folder?
As mentioned by nc50lc above, you can also rebuild and rescan databases.

If you did so but it didn't work, post the logs, so we can know what's causing the problem. You can find the logs in "armorylog" text file.

Walletexplorer can't be helpful here.
Walletexplorer put different addresses in a same wallet if they are co-spent in a transaction. For example, if you make a transaction and use addresses A and B as inputs of that, then both addresses go to a same wallet. This is all they do and there is no way they can know which of addresses is the change address.

To mine a block, miners must solve a proof of work problem.
As the proof of work problem is solved through brute-force method, there is no way to know when exactly it will be solved. Given the difficulty of the proof-work problem, we only know that blocks are mined (roughly) every 10 minutes on average.
If the fee you pay for your transaction is high enough, your transaction will be included in the next block. But the time it takes for the next block to be found does't depend on the fee you paid at all. In the case it takes 1 hour for miners to find the solution, you have to wait 1 hour even if you have paid a very high fee.

Take note that even if you delete the files, they are not permanently gone and they may be still recoverable using some recovery tools.
When you delete a file, it means that you no longer need that file and your OS hides that file. The file exists until it's overwritten by some new data.  

You are wrong too.
The block time isn't exactly 10 minutes. Blocks are mined (roughly) every 10 minutes on average.
A block may be confirmed a few seconds after the previous one. It's also possible that it takes more than an hour.

I would move the wallet file to the default location too. But note that you don't have to move the backup file to the default location. You can move the backup file to any location you want.


There is no difference. Both can work as a backup.
When you click on "Save backup", electrum actually create a copy of your wallet file.