Can we find 100% probability region in an orbital if the position of an electron is limited by speed of light?
The (Wave)functional forms for the surface which contains the 100% probability for finding the electron extends to the literal edge of the universe.  In the context of 'wave' it is nonsensical to measure an electron's position, and hence its speed may not be determined.

In the context of particle, an electron, having nonzero mass, may not be accelerated to the speed of light.