Well, an FRL-M does allow permite you to work, but yes it isn't a work permit. Yes there are limits on the amount of time you spend outside of the UK if you intend to apply for an IRL. If I remember correctly, you can't spend > 90 days outside of the country, unless there is a good reason for it (like keeping your employment in the UK). But there are no limits on the number of times you can come and go out of the country under the FRL.
Also, the all caps is kind of annoying.