Yes my understanding for ARC is this is for overcoming inadmissibility, so once it's granted, the person will be admissible to Canada again. You'll still need to apply for TRV to visit Canada everytime TRV is expired or until becoming a PR, but you don't have to apply for ARC again, these is why it give two categories 1) for PR and 2) for time to time applicant - the one needs TRV or non PR from a visa-exemption country. Because once inadmissibility is overcame, the person will be free to apply any visa or PR to Canada, you'll still need to show your ARC paper everytime entering Canada though so don't lose it, keep it with your passport.
Again, it is because ARC is a pardon for the applicants the past bad immigration history in Canada, this is why it is so hard to get one, and why a compelling reason is so critical.
For communicating with VO, I guess different VO has different ways. I was emailing Beijing from beginning, it took near 2 weeks for them to reply my first email request but after that, they signed a case number to my email (showing in the email subject line), they were pretty fast, would reply to me in 48 hours. But I have to say once I emailed them our ARC application package they stopped replying to my further request but simply emailed the ARC paper in PDF to my husband's email address on file once it's granted. But needless to say send your VO a email to follow up wouldn't hurt