Currently I removed the old vinyl floor, and found the old black adhensive on the plywood floor is very difficult to remove. After asked several guys, the current plan is applying a thin layer versabond fortified thinset on the old adhensive with flat trowel side, then putting a wonderboard cement board on that and nail it on the wood floor. Is this plan ok??
after I read the instruction on the versabond, it said it can be used on cutback adhensive, does it mean I can directly apply the ceramic tile on the thinset mortar without wonderboard? thanks for any info.

That would depend on your subfloor system, but even if it "technically" okay, I would still use a 1/4" cement board.

Basically, you must have two layers of plywood with a total thickness of 1 1/4". Most floors do not have this.

Even with two layers, you're depending on the bond between the thinset and cutback adhesive. A cement board with thinset underneath, nailed/screwed into place, is your best insurance for a successful installation.

Is your current subfloor plywood, and do you know the thickness of it?

The correct way to install the wonderboard is to apply a fairly wet versabond on the plywood with a 1/4 inch notched trowel and set the wonderboard into that then nail or screw it down. This eliminates the potential for voids or humps that you would get with a skim coat with a flat trowel.

Tiling directly on cutback adhesive is fine with a good modified thinset, but like K-man said, the subfloor needs to be rigid enough.

Yes, I think it is plywood, I can see it consists of about seven thin layers. it is about 7/8"

Most likely it is a single layer of 3/4" ply. You'll need a CBU for that.

Also important to check out your joist system to make sure it's up to par. Use the "maximum span calculator" at the top left of the page. Are the joists on 16" centers?

Do I need to wait versabodn dry before screw it down?

yes. joists is 16" centers. Sorry, I am really a newbie to these stuff. what is CBU? and I checked span calculator, lots of stuff I am not sure which I should select.

No problem. If everybody on the site was a pro, we'd have no questions to answer.

Go ahead and give us the specs on your joist system. We need to know the size of the joists (2x8, 2x10, etc.), the species (SYP, Fir, etc.) which is usually stamped on the joists somewhere. There should also be a grade stamp on there, which is a number. Then we need to know the longest unsupported span of the joists. Simply, this is the longest span that your joists run with no support from underneath them. There may be areas of your house that won't be getting tile, and those don't matter. But if a soon-to-be tile area is over a joist, we need to know the unsupported span of that joist.

CBU = Cementitious Backer Unit, or cement board. It's referred to by many different names, usually by the brand name: Hardibacker, Durock, WonderBoard, etc. The thinset underneath needs to be freshly combed out and the CBU set into it immediately, then screwed/nailed down immediately. You can start tiling over it as soon as you're finished screwing it down, no need to wait.

the only stamp on the joist I found
"A.F.RA 43
S-P-F SEL
S-DRY STR"

and longest unsupported span is 140" and it is 2X7“

So you have two by eight joists. SPFsel stands for Spruce pine fir select structural. S dry means it was kiln dried to 14% moisture. You're ok for span, though if you have easy access to the floor system you could install a couple of lines of solid blocking between the joists to stiffen things up a lot.