bitcoin-cli getnewaddress can i customize my address start through getnewaddress?

for example instead the address start with 1asdjIOAWJRA

i write getnewaddress 1xxxx then it continues as it wish

also what's the difference between addresses starting with 1 and addresses starting with 3?

can i choose from bitcoin-cli to get my address starting with 1 or it must be random and can be started by 3 while i dont wish that?

the reason of the need to customized addresses to make sure that it really creates this offline addresses instantly and is not in a hidden database installed while installing the bitcoin-cli
That is called a vanity address, and Bitcoin Core does not support generating vanity addresses. In order to do that, you would have to find a vanity address generator (separate piece of software). But then, you have to audit the code to make sure it is not doing anything funny with your private key. Bitcoin Core is open source, so you can audit the code that generates the keys if you want.

The address prefix denotes the type of script the address encodes. A bitcoin address that starts with a 1 is a Pay-to-Pubkey-Hash address, and a 3 is a Pay-to-Script-Hash. See Address Prefixes 

You can change the type of address the cli generates by passing an optional argument to getnewaddress see RPC Docs - getnewaddress:

bitcoin-cli getnewaddress "label" "address_type"


address_type options are "legacy", "p2sh-segwit", and "bech32"