Mostly swaps, might venture into staking and liquidity pools. Liquidity pools is lending/borrowing in de-fi right?
Sorry for the delay, I forgot to revisit this topic
Liquidity pool is different from lend/borrow
Liquidity pool you provide liquidity in 2 different coin for those who swap between these 2 coins
Lend/borrow you offer some currency to borrow some.
For example, you lend BTC to borrow USDT
- Example 1, I change the default max/unlimited value to 100 value so I do not have to spend gas fees in future to revoke this. The worse case scenario that can happen in future if I do not revoke this 100 value contract is max I can lose is $100 from a hack not a $million from my wallet address, basically I lose $100 from a $million if I do not revoke?
Exactly, you got it right
In this case only 100 dollars would be at risk
- You mentioned If the contract defaults to unlimited approval, is this still possible after I set the value with the 100 example I gave above, my 100 input value defaults back to max/unlimited again?
If you set a limit of 100, you'll make a tx and this transaction will only be on the 100
In a future transaction with the same contract you need to set it again to the desired value
- Who decided in the De-Fi world that the default input value should be set to unlimited/max and why? Who programmed this value? It is like for example banks giving their customers unlimited/max no withdrawal limits at ATM cash machines meaning if a thief has access to the debit card and there's a $million in the a account then the thief can empty all the cash from the cash machine and go onto the next cash machine and empty out and so on until balance goes to $0. It is an absolutely insane idea whoever thought of that max/unlimited input default value in de-fi. I hope there is a update to MetaMask wallet to auto adjust the default value for you for all de-fi transactions and if there is no incentive to do this then who is truly running De-Fi? Scammers/Hackers? Or they do this on purpose to collect more gas fees in de-fi from revokes.
I think they leave it at unlimited to save on fees
Some networks are cheaper, but you have to remember that transactions on the ETH network can be very expensive, and a simple transaction to approve a limit can cost several dollars, for example, making it expensive to make many transactions.
- I understand theres smart contract in de-fi that involves on-chain meaning gas fees to use the chain however Smart Signatures are supposedly off-chain meaning no gas fees so why it costs gas fees to Revoke a Smart Signature 
I can't explain this part exactly, but to revoke through revoke.cash you have to make the transaction