I counted bitcoin address length, it is 34.
Is this all the same always?
No, they can be as short as 26 characters eg
11111111111111111111HeBAGj
to as long as 34 for P2PKH addresses (addresses that start with '1')
P2SH (testnet) addresses can have up to 35 characters IIRC.
Bech32 segwit addresses can be as low as ~14 characters long eg
to as long as 74 characters.
And how about other coin's case?
It depends on the encoding being used by the coin to generate addresses.
If same coin, address's length is always same?
No, they have the same RANGE but they're not always the same length.
The encoding provides the range of values that generates a valid address.
In some cases however, the address lengths are always the same because of the way addresses are derived.
For example Ethereum addresses are always 40 characters long (plus the 0x prefix to give 42 chars) because it's the last 20 bytes of the SHA3 hash of the public key controlling the address.
