I still have my mobo for the i5 4690k. but what should I get i5 4690k vs i5 6400-6500 vs i5 7400-7500. and what kind of mobos will work for the i5 6400-6500 and i5 7400-7500?
Yes, however to get it to work with Kaby Lake you'll need to make sure that mobo has the proper BIOS to support it.
will ddr3 ram work with the i5 6400-6500 and i5 7400-7500 . or do I need ddr4 ram?
You'll need DDR3L memory or DDR4 (do DDR4). So no, regular DDR3 won't work. (Technically it will, but it will burn up your memory controller REALLY quickly.)
Yes, however to get it to work with Kaby Lake you'll need to make sure that mobo has the proper BIOS to support it.
will ddr3 ram work with the i5 6400-6500 and i5 7400-7500 . or do I need ddr4 ram?
You'll need DDR3L memory or DDR4 (do DDR4). So no, regular DDR3 won't work. (Technically it will, but it will burn up your memory controller REALLY quickly.)