If I use Tor to access "regular" internet sites, like Yelp, Amazon, and others to leave reviews, will I be I 100% anonymous? (Without changing my IP and MAC addresses?)
The short answer is "maybe". It depends on what you've done in the Tor browser, and what forms of anonymity you're trying to achieve.
For example, if you sign in to a site (say, to leave a review), the site won't be able to tell where you're signing in from (which it normally can deduce from your IP address), but it will certainly know who you are, at least to the level of your account details (because you just signed in with that account). If you avoid signing into anything, you will theoretically be anonymous, but if you move from one page to another, there's still always a risk of a pattern being recognized (even though the requests come from different IPs and in theory you won't be picking up tracking cookies or anything) if, for example, very few users would be likely to visit those specific pages using Tor within a narrow timeframe (Tor exit nodes - the IP addresses that servers see when you use Tor - are generally well-known, so you can hide which Tor user you are but you can't hide that you're using Tor). True anonymity is hard.
Not directly relevant to your question, I think, but you should be aware that security and anonymity are not the same thing. A breach of security (for example, due to a bug in the Tor browser, which has happened before) can lead to a breach of anonymity (for example, by fingerprinting your computer and sending that data to another server, or by sending a network request that is not routed through Tor and hence reveals your real IP address). Security breaches can also lead to other things, like logging keystrokes, accessing files on your machine, infecting other programs, sending email to all your contacts, and so on. The Tor project takes security quite seriously, but it's also a very tempting target - lots of people looking for ways to compromise it, and see what its users are up to - and there's no such thing as being "100% secure" with any piece of software as complicated as a modern web browser.