Hi, im new here and I dont know what is NMS and unrestricted, I know what is OOB and I can figure out what skipless is
Unrestricted depends on the game, usually it's completing something without any restrictions on glitches, or a certain in-game item, or other exploits. Make sure to check the game's rules and category rules.
NMS, as far as I've ever seen, just means 'No Major Skips' and means one or many major glitches, exploits, or indeed skips, have been banned from that category but might be allowed elsewhere. Again, check the category and game rules for exactly what the category is forbidding.
If you do want to know exactly what's different about these categories for a specific game you can always try asking in the community, or a moderator directly failing that.
So for that instance, they do explain it within the Category Rules when you are on a leaderboard with that option selected. They list a No Major Skips as "Tricks that do not skip entire missions, and that save no more than 30 seconds are permitted. Skipping sub-missions, such as collecting flashlight in daycare, are allowed. Going Out of Bounds, or using deloads in any way shape or form, are banned."
I'm sure the routing guides have routes designed to skip any tricks that meet those criteria btw