l used my car to do a jumpstart on my sister is car but the jumpstart was connected wrong (positive to negative and vice versa to her battery). Her car would not start of course because of the wrong connection, however within minitues, the jumpstart cable became really hot and l saw a little smoke came out of my car. Will my car be okay? or will it damage to any other part of engine?

you probably will be replacing an alternator real soon on it,id say the smoke you seen was from it,id have it checked just to be sure,anytime you see smoke coming from one when you try and jump start it ,its not good news,you may also have a very dead battery in the morning,if it is not already dead,the rest of the engine should be ok,but doing that can damage certain electrical parts in it,so have it checked to be safe about it,good luck on it.

Unfortunately, many of the car is electronics are probably fried. What is worse is that there is no simple way for a dealer to troubleshoot which assemblies have fried and just start replacing things in mass and it becomes very expensive.

Lexus electrical systems have safety devices called, fusible links. You probably blew a bunch of fuses and maybe, the onces that are not protected, some ecus. Have your vehicle checked out of you start having problems, or for preventive maintenance.

you might even have drained the battery.

it would be better to buy a new new battery and all electric wires for your car