Flooring Tile - self leveling mortar mix

I need to put down ceremic tiles that are 12"x12" in a basement bathroom.
The existing floor has an existing linoleum (?) square tiles that were glued on and not completely flat in all places (the new tiles rock a bit when I lay them down flat). Plus I have some sections of the floor (concrete) that we dug up for new pipes and then smoothed out flat to the existing tiles.

Can I pour self leveling mortor mix over everything to level things out? THe existing tiles are set pretty well and not loose. If yes, how liquidity is the leveling mix normally? Is it like a thin soup or like mash potatoes in consistency? What's the minimum thickness?

Also, what is the difference between thinset and mortor? I've used thinset in the past from homedepot and it's a glue adhesive. Is mortar more like a concrete/cement mix?

First remove the vinyl and the glue.:)

Make sure your tiles are not asbestos if you are going to remove them. If they are asbestos, it is best to keep in place. That said: leveling compound. We have recently used leveling compound (Henry) and found that it is not something you can just pour on. You must use a trowel. The consistancy was more like pancake mix. I mixed according to the instructions. It was harder to level than I thought it would be. It took 3 coats to get it even enough in the bathroom. We used the additive for feathering for that. Next time we tried it we decided to use without additive for feathering. I don't know if it was easier because we had now done it 3 times previously or if mixing without additive is just easier to make level. But we finally got the hang of it. It still took a few coats.

SLCs will not work over the tile or the cutback adhesive under them if this is what is there, also you have to mix SLC strickly to what it says on the label for that product, the floor must be primed and wire lath used if over wood, you pour it and help it in the first few seconds only into corners if need be, then you leave it ALONE, don't touch it, or try and play with it, don't add any more or less water than instructed, it will level itself out.:)

I'm thinking the consistency must be very liquidity for it to automatically settle into place and let gravity even things out (like water heading for low spots rather than stay at high stops)?

As for the existing tiles, I've removed tiles that are loose. The rest is firmly embedded. Can they be left alone as to minimize work/time?

NO, if you want to leave this stuff, you will have to do a full mud job over this floor, with a slip sheet [tar paper] and wire lath, this what I would do anyway, if it's way out of level, 1 1/4" of mud.:)

Like I said earlier, SLCs will not work over the tile and the glue.:)