in gel filtration separation depends to high extent on the shape of the beads and the pores in it. since high pressure can cause distortion of the shape of the gel beads it might be hazardous for the separation, however mild pressure that can maintain solvent flow nearly similar to gravitational one is acceptable.
No. The AKTA Prime and Prime Plus are limited to 1 MPa (10 bar, 145 PSI). This is far too low to effectively pack or run a size exclusion/gel filtration column.