An R&R is rarely going to be "Change a character's name." R&Rs are when an agent loves something about a book, but thinks it needs a major change to work, and either that change is so drastic that they'd never trust giving rep to the author without seeing it done first, or it's the thing that's keeping them from fully falling in love with/seeing the book as salable.
Agents will often ask for revisions after they offer rep, but these are usually revisions that they feel they can trust this author they haven't worked with yet to handle. Or possibly they are just so enthusiastic about the book that they will take the chance on the author, despite major revision needs.
As for examples of big revision suggestions or requests, I've had agents/publishers ask me to change the POV character for the full book to a different character, to cut the main LI and change to the secondary one, to change age categories, to cut 20K from a tight book, to add 50K to a book (which was admittedly short), to change the MC's motivations and therefore everything that happens in the first 3rd of the book... I've also had vague requests from definite R&Rs, such as the voice isn't working or the pacing needs to be fixed, without details given about what that agent was actually looking for.
Plan that your book will not be published as-is unless you self-publish. It is rare these days to find agents and publishers who don't ask for changes. Don't go in with that hope that it will be published as-is.