I've been curious about why transaction had to deal with spending of all inputs on a particular address.
Although I'm not new to the fact that all transaction have to be spent in a single output buy why does it have to work that way??
So the change I'm receiving can I call it an output or a new input ??
If it's not on a new address but on the same address(the received UTXO), will it be counted as part of inputs along with other input when I want to send again to a new address.
No you don't need to use one single output you can send a transaction to mulitple different addresses if you're using Electrum for example. And if you send several UTXO to one address, you will be able to treat them one by one for sending them elsewhere if you're using such kind of wallet