Base coat
 

I have applied 3 coats of base coat on tail extension.
Can I or should I sand the base coat before applying the clear coat? If yes, do i wet or dry sand?

If the base has been on it less than 24 hrs. you can probably clear it without sanding. Check manufacturers product sheet.
If it's a metallic base and you decide to sand it, wet sand with 800 and apply a couple more coats of base before clearing it. Otherwise the sanding will mess up the metallic and it WILL look bad when the clear goes over it. If it's non-metallic you can sand it and clear it, so long as you don't cut through.

It is metallic so I will go straight to clear.
Thanks for the reply.

No base coat ...metallic or solid color should be sanded before clear coat. If base coat is full of fish eyes or dirt...let it flash off for 30 minutes at 70 degrees and sand smooth with 600-800 and recoat with 2-3 more coats of base or until coverage ....then let flash and clear coat.