In the SPECIAL column in the Cleric spell list it does not show "M".

Then when I go into the spell itself it shows "M".

This is true of a number of spells in the special column in spell lists.

Is the special column in the spell list of any use if I have to go into each spell to find out the requirements?

Quote from DarkStranger1066 >>

In the SPECIAL column in the Cleric spell list it does not show "M".

Then when I go into the spell itself it shows "M".

This is true of a number of spells in the special column in spell lists.

Is the special column in the spell list of any use if I have to go into each spell to find out the requirements?

The "M" in the "Special" column on the spell lists doesn't just mean it has any material component; it indicates that it has a specific material component that you have to actually have in order to cast the spell (either because it has a cost listed, or it's consumed by the spell, or both). This is stated in the paragraph above the spell list. The point of this is to highlight spells that you need to actually have the material component for and can't use a spellcasting focus for instead.

While this spell does have a material component, it doesn't have a cost and it isn't consumed, so there's no "M" listed. 

Can no longer be used to repair constructs. Only difference.
So basically, where this was incredibly useful for an Artificer with a Defender before, now it is incredibly less so.

Quote from TheChangelingEmperor >>

Can no longer be used to repair constructs. Only difference.
So basically, where this was incredibly useful for an Artificer with a Defender before, now it is incredibly less so.

I don't think that's true. It doesn't say it can't be used to repair constructs, and the description of the Steel Defender feature still explicitly says that if this spell is cast on it, it regains 2d6 HP. That still applies.

Also worth noting that with the 2024 update, all of the normal healing spells can now be used to heal constructs as well.

I've heard before you can use Mending on a corpse to reconnect severed limbs (or even a head), since a corpse is an object and a severed limb could be considered a break or tear in it. Then after Mending the corpse, you can use Revivify or Raise Dead to restore a PC with all restored limbs since Regeneration spells doesn't come into play till 15th level. Is this legit?

Quote from Suthos >>

I've heard before you can use Mending on a corpse to reconnect severed limbs (or even a head), since a corpse is an object and a severed limb could be considered a break or tear in it. Then after Mending the corpse, you can use Revivify or Raise Dead to restore a PC with all restored limbs since Regeneration spells doesn't come into play till 15th level. Is this legit?

The notion that a corpse is an object is somewhat debated; the idea that you can do to a corpse things that you can only do to objects doesn't generally appear to be the intended interpretation of the rules.

That said, if you're willing to consider a corpse to be an object, with all the follow-on effects that that implies, then it seems like you can technically do this as long as the cut/break/etc. isn't more than a foot wide.

Quote from Suthos >>

I've heard before you can use Mending on a corpse to reconnect severed limbs (or even a head), since a corpse is an object and a severed limb could be considered a break or tear in it. Then after Mending the corpse, you can use Revivify or Raise Dead to restore a PC with all restored limbs since Regeneration spells doesn't come into play till 15th level. Is this legit?

According to the 2024 PHB, within the rules glossary:

"An object is a nonliving, distinct thing. Composite things, like buildings, comprise more than one object."

Well, a corpse is distinctly a corpse, which are famously known for being not alive. I'd say it's more clear cut than ever in this edition. Also, if you want to use Revivify on a fresh corpse you plan to mend, you must first cast Gentle Repose! By the time you've finished casting Mending (which takes 1 minute), the time frame for Revivify to work will have already passed.