Abdussamad thank you very much for this, to add on your reply the ''remainings'':
2: As wallet id, I meant ''address''. For receiving case, you told me I need to share the address to which I want to receive bitcoins. But what if I want to receive the bitcoins funds to address I have never used before? For this I might need to create new address BUT you told me I cannot manually create address (neither one nor more) within electrum. However you said I always have 5 unused ones. This word ''always'' got my attention. Since you were saying so, I assume as soon as I receive ANY bitcoins amount to ANY address, NEW unused address (never been there yet in my electrum) will Automatically occur. Is this correct or not?
Electrum tries to ensure that you have unused address equal to your gap limit. The gap limit is 5 by default. It means if you receive bitcoins to an unused address then electrum will generate a new one to ensure that you have 5 unused ones. If you receive bitcoins to an address that has previously received bitcoins then obviously there is no need to generate new addresses. They were already generated when you received bitcoins to that address the first time. I hope you understand.
If correct then something needs to happen to either of other addresses - to either the address which got the bitcoin payment and caused (assuming what I previously asked is correct) new address to automatically occur (if to this one, what happens with received payment?) OR to any other one (e.g. the one that has zero balance). Something happens here to old and/or used address otherwise new address wouldn't occur?
Electrum monitors transactions and creates new addresses like I described above. That is all that happens.
5. Once again assuming my understanding about ''Automatically occur'' above is correct: Since I cannot delete addresses, this means as long as I will actively use electrum, the list of addresses will only raise larger and larger? Obviously I am referring to the RECEIVE tab and Not History tab. In the History tab, its logical the answer on this question is positive but not so logical for RECEIVE tab, thats why I typed this.
Yes it will but addresses that you have spent from are tucked away under 'receive' tab >'main account' > 'used' to reduce clutter. In case you are wondering you can still continue to use them to receive or send bitcoins in future.