Casinos can lower/increase a slot machines payout at will
It is possible but in reality, it hardly ever happens. If a casino wanted to change the payout of a slot machine, they would have to completely change the computer chip in the machine. The payout percentage is programmed at the factory and if a casino wishes to change it, they would have to complete loads of paperwork, consult with the Gambling Commission they are responsible to and have witnesses present for the whole process.
If you bet with more than one coin, your odds of winning increase
Betting with more coins only increases the amount you win not your chance of winning.The RNG has no idea how many coins you have bet. The number of coins you bet is measured by a separate computer chip that does not communicate with the RNG. And as the RNG controls the outcome of a spin, betting three coins on a spin instead of one does not increase your chances of winning.
Casinos can reward loyal players with jackpots
If a casino was to do this, they would quickly be closed down. It is completely illegal for anything other than the RNG to determine the outcome of a spin or dictate when a jackpot is awarded. Also, there are plenty of examples of players playing at an online casino for the first time and winning life-changing amounts of money.
The payout percentage is 95%, I will get back $95 of every $100 I bet
Although theoretically possible, it would be unlikely to happen. The payout percentage of 95% is based over a very long period of time. Longer than anyone could conceivably sit at a machine and play on a slot machine. It is therefore more likely that you will either win less or more than the 95% payout percentage.