Can I still use Paypal eventhough I haven't used it for a long time?
Yes
Can I still receive and send payments even tough it's not link to any bank account?
Yes, but - you will have limits on sending, receiving and withdrawing funds.
Is there any other things I need to verify aside from the email that was sent to me when I sign up here in PayPal?
You should ensure that you "verifiy" your account - link and confirm both a bank account and credit card - then you can use your account as intended.
Does anybody knows how much is the fee for withdrawing fund from Upwork to PayPal account?
Suggest that you contact Upwork with you concerns as we don't know how you are linked to them.
I have this one client before, probably the last client I guess, and he can't send me the money to my account. What do you guys think might be the cause of that problem?
No way to know - Does your client have a US PayPal account ?? Is his account setup properly ?? Does he have your correct email address ?? Is your account email address confirmed ?? What is the status of of the transaction on your client's end or is he or she seeing an error message ??
Would PayPal notify me if there's a fund that is trying to get in my account?
Yes, you should get an email notification and a notice in your account Activity section.
Or would Upwork notify me if they can't send the funds to my PayPal account.
That's depends on Upwork.
I was trying to email them while ago but I can't find the option to do so. Is their any way I could reach them through email?
You would have to do that outside of your PayPal account.
