To conceive seed (eis katabolēn spermatos). For deposit of seed. See Heb 4:3 for katabolē.
Past age (para kairon hēlikias). Beyond (para with the accusative) the season of age.
Since she counted him faithful who had promised (epei piston hēgēsato ton epaggeilamenon). Sarah herself (autē-Sarra). Even Sarah, old as she was, believed God who had promised. Hence she received power.