Q1: I made changes to the DNS record, but my PC keep getting the old IP for the record.
A. Either your browser, PC or the name server that your are using is caching the DNS record. Firstly, you can either refresh the DNS cache from your PC or just reboot your PC.
Browser do caching DNS record, to flush the DNS cache from your browser, restart your browser, or install some DNS cache management plugin.
To flush the DNS cache on your windows PC, use the dos command below
ipconfig /flushdns net stop dnscache net start dnscache
If above not working, most likely the name server(s) that your internet provider is caching the entry. You might either want to wait until it flush itself or change to use other name server like opendns.com.
Q2: I’ve subscribed a web hosting account from webhost.com, how to configure the DNS so that user can browse the web from webhost.com rather than browsing my NAS? But I still want to be able to access my NAS using nas.mydomain.com.
Simply create/update the following DNS entries for your domain:
Record Type: A
Domain name: mydomain.com
Record Value: <I.P. address of your myaccount.webhost.com>
Record Type: CNAME
Domain name: www.mydomain.com
Record Value: <myaccount.webhost.com>
If you not sure about the record value, consult your web hosting support team.