Exchanges do not work like that, I do think you have to understand the fact that they try and when you place an order they sell that order to some customers waiting to buy, but when you think about it many of these exchanges are 'instant' , so at that time they just try and just match these things instantly. Their name is
EXCHANGE itself, they just exchange and take their commission between buyer and seller.
(A little image from google to show what they do)
Regarding your other questions.
1. Fake Volumes is very normal and many of these exchanges try and even produce fake whale alerts.
2. They cannot give more cryptos than they have, since most of these Ath and BTC they can be exchanged and sold , traded in a couple of seconds , if that's fake it can never be done, they will force you to hold your coins for a while.
3. Reportedly 95% of the volume in Bitcoin exchanges are fake according to a recent study (
https://www.google.com/amp/s/qz.com/1578753/common-clues-that-a-bitcoin-exchange-is-faking-its-trading-volume/amp/)
They can fake Volumes but they won't give you fake crypto ! Well the normally good exchanges won't.
[Another image taken from google]
` Now this is how it works normally, the exchanges collect the most data and then they just use their immense customers to match the seller and buyer and web them together. So this is way faster and works well. They even use their bank accounts to help and buy and sell them.