Q: I want to use both Robots and Bio-thralls but I can't build the other once I have both researched how do I fix?

A: When the Robots or Bio-serfs technology is researched it sets your last built species to robots in the case of the Robots tech or bio-thralls in the case of the Bio-serfs tech. To build the other I recommend you finish building the first assembled species before you start researching the other then once researched look to your Capital world for the Design [bio-thralls or robots] decision. This will set your last built species to said species (This will not get rid of any templates you may already have).

Q: I want to upgrade the birthing Chambers Higher but I can't and I have the higher level

A: You need to outlaw robots to upgrade the birthing chambers. this is for balance reasons. As if I did not do so normal empires would be getting a build speed of up to plus 8 with the robot building.