You do not need COSMO-RS to do ADF calculations with continuum solvation (see COSMO vs COSMO-RS FAQ). If you want to calculate thermodynamic properties like partition coefficients, VLE, solubilities, etc. you do need COSMO-RS. COSMO-RS usually also yields more accurate solvation free energies and pKa values than COSMO.
In principle, yes, but your are advised to rerun the COSMO calculation with ADF. Since ADF uses a slightly different procedure (gas phase optimization followed by COSMO calculation with an infinite dielectric constant) as well as different technical settings (basis set, integration, surface charge generation), our COSMO-RS implementation has been reparametrized specifically for use with sigma profiles generated in that way. Therefore you are advised to follow the set procedure in ADF, easiest is to use the COSMO-RS preset in the ADF GUI. See for details: C.C. Pye, T. Ziegler, E. van Lenthe, J.N. Louwen, An implementation of the conductor-like screening model of solvation within the Amsterdam density functional package. Part II. COSMO for real solvents, Can. J. Chem.87, 790 (2009) If you do insist on using sigma profiles generated with the other programs with different defaults, you can use the cosmo2kf utility to convert the plain ascii cosmo files to our binary file format. There are also scripting tools for COSMO-RS to facilitate screening solvent (combinations) for activities, partition coefficients, VLE, etc.
With your SCM User ID and password you can download the compounds database manually as explained in the manual.