Can we use a buyer account and a seller account on the same PC and internet connection, or is there any issue?
No issues, just not 2 seller accounts without approval. I have a personal, business, and seller account on same pc and same internet.
Its fine. I have also logged into SC from many different states and countries because I live life on vacation. Just got back from a 30 day roadtrip so logged into SC from a different hotel almost every day. I rarely use a VPN or my mobile network.