"Can my transaction be canceled or reversed?"
Short answer: no. Even many advanced cryptocurrency users can recall an incident when they failed to double-check their transaction details and they accidentally sent funds to the wrong recipient, or sent the wrong amount. As unfortunate as it is, cryptocurrency transactions on the Bitcoin, Ethereum, and Bitcoin Cash networks are designed to be irreversible and no one has control over them.
To learn more about why bitcoin transactions can't be canceled and how this aspect of bitcoin and other similar cryptocurrencies compares to other methods of payment like credit cards and cash, check out this blog post on Bitcoin Transactions & Chargebacks. 1
"How do I recover from a cryptocurrency scam?"
You don't. At least, you don't recover your money. I guess you recover by learning from the mistake and doing things more safely in future. It may be worth asking an accountant if the financial loss on your investment can be offset against other taxable income.2
"Is it impossible for local police or anyone to recover my money?"
In most cases, any loss less than $100,000, the police are likely to only hand out advice. It isn't worth their while to try and investigate most cases where people willingly give their own money to unknown people in faraway countries. Foreign police forces often just ignore any requests for help in such matters. However plenty of scammers will offer to help you. Ignore them. I hope you are able to put this behind you and move on.2
"What happens if my transaction is never confirmed?"
If a transaction goes unconfirmed for too long, it will eventually disappear from the network.
Most clients will remove it from their pool of unconfirmed transactions at some point. When most clients have removed it, you can go ahead and send the transaction again, this time with a higher fee. There's not a precise time when the transaction will disappear from the network, it could be days or up to a week. This is why it's always recommended to set a transaction fee.3
"Can I broadcast a fake transaction over the blockchain?"
It is possible to broadcast a fake transaction but it would never appear on the blockchain. Although you broadcast it (broadcast means sending out), not a single node would accept it as valid, and thus it would never make it into a mempool (mempool means the list of VALID TRANSCTIONS that might be added into a block if a miner picks it up).4
- Beware of any software that makes claim of sending fake bitcoins/transactions. They are nothing more than malwares. First they will make you pay for their software and then attempt to steal your bitcoins.
"I've been waiting for X days and my transaction is still not confirmed?"
This is a common problem that can frustrate new Bitcoin users, but it's not an unplanned bug that you are experiencing- Satoshi placed a limit on the size of Bitcoin blocks, which are mined every 10 minutes on average. This protects the decentralized node network from being flooded/DDoSed, and creates a "highest bidder" market for new data (such as your transaction) being recorded to the blockchain. This design limit means that the fee your transaction pays does not depend on the value of the transaction you send, it depends on the size of the transaction you send, measured in vbytes.
I have already discussed the method on how to use Electrum to add fees to an unconfirmed transaction in this thread: https://flaw.tech/d/27-using-electrum-to-add-fees-to-unconfirmed-bitcoin-transactions