I worked in one bike i adjust the brakes and the gears but is do weird shift The RD. Is up shift fine the RD in all ten cogs but when i down shift all 9 cogs downshift very smooth but when i downshift before the chain go in the smallest cog is do like skip then go on the smallest cog. The chain is looks good. The RD is tiagra is can be RD problem or somethink else.

Hard to understand your post, but it appears that your high gear limit screw needs adjusting; if the indexing is smooth on all but the outermost cog (when all tension is off the cable), the only adjustment affecting the shift is the limit screw. If it is sluggish in this shift to the smallest cog in your rear cassette, the 'h' limit screw is likely too tight, and would need to be backed off and turned counter clockwise.

You've got the words wrong.
Upshift = go to a higher, faster, harder-to-push gear.
On the rear this means going to a SMALLER sprocket.
Unless you have a kinda rare low-normal, rapid-rise derailer (and Tiagra were never made like that) the power for the upshift comes from a spring in the derailer, pulling the derailer sideways, towards the smaller sprockets.
The shifter only feeds out cable.
On your description my first suspiscion is that the cable isn't sliding smoothly.
You can work through the whole cable run, looking for contamination, corrosion, kinks and poorly seated sheaths, but sometimes it's more time effective simply to redo the whole thing.

There are other options too, but sticky cable is the most common.

And make sure that the cable housing ends are properly prepped (ground of filed flat and with no protruding wire strands)and appropriate ferrules installed.

I'm going to agree that a sticky cable housing is the most likely cause of your problem. Bad cable housing end prep would result in not being able to access the biggest rear cog dependably. One other possible issue is a mis-aligned derailleur hanger. With a 10-speed cassette the alignment has to be really precise.